Just wanted to share my experience with WiFi Calling. I am in the US on T-Mobile and WiFi calling has been working for me surprisingly. VoLTE has also been working wonderfully. I've tested this on a Global Mi 9 running Stock and the Xiaomi.eu rom.
Enter these codes into the Dialer to enable the options in Settings. (Settings < SIM Cards & mobile networks < Sim Card Settings < VoLTE Enabled/Make Calls using WLAN)
VoLTE *#*#86583#*#*
VoWIFI *#*#869434#*#*
Things should work after you enable the two options. This depends on whether or not your carrier supports it and your e911 address set (US only?).
Some issues you might run into is that the option for Network Preference is greyed out and you will unable to change that option. I've had some success if you disable it and re-enable it and click on that option really fast, it will go through. When you first enable VoWiFi, it is important that you get into this menu and change it to WiFi preferred or WiFi Calling won't work.
UPDATE:
Manually creating your carrier APN worked great for me. Been testing it for about 2 weeks and I haven't had any issues with VoLTE/VoWiFi. For example, for me on T-Mobile, I created a new one with the following settings. The important part I'm guessing is the APN type. Also make sure that your carrier has enabled WiFi Calling on their end as well.
APN: fast.t-mobile.com
MMSC: http://mms.msg.eng.t-mobile.com/mms/wapenc
MMC : 310
MNC: 260
APN type: default,supl,mms,ims,cbs
APN protocol: IPv4/IPv6
APN roaming protocol: IPv4/IPv6
On a side note, since you're on T-Mobile US, are you getting LTE+? I was showing LTE+ on my Mix 2S and Mi 8, but doesn't show up on my Mi 9.
Can verify, works with Chinese Mi 9 8GB 128GB version. I'm also on T-Mobile. Now there is "HD" written on the signal icon.
---------- Post added at 08:24 AM ---------- Previous post was at 08:22 AM ----------
Ulver said:
On a side note, since you're on T-Mobile US, are you getting LTE+? I was showing LTE+ on my Mix 2S and Mi 8, but doesn't show up on my Mi 9.
Click to expand...
Click to collapse
It does when I'm outside. RN it isn't showing tho, I'm in the basement. I'm pretty sure I've seen it before when I'm on the bus or something
Also works in Netherlands with Vodafone
lightcao said:
Just wanted to share my experience with WiFi Calling. I am in the US on T-Mobile and WiFi calling has been working for me surprisingly. VoLTE has also been working wonderfully. I've tested this on a Global Mi 9 running Stock and the Xiaomi.eu rom.
Enter these codes into the Dialer to enable the options in Settings. (Settings < SIM Cards & mobile networks < Sim Card Settings < VoLTE Enabled/Make Calls using WLAN)
VoLTE *#*#86583#*#*
VoWIFI *#*#869434#*#*
Things should work after you enable the two options. This depends on whether or not your carrier supports it and your e911 address set (US only?).
Some issues you might run into is that the option for Network Preference is greyed out and you will unable to change that option. I've had some success if you disable it and re-enable it and click on that option really fast, it will go through. Another thing is that WiFi calling might glitch out if you have cellular on. It just randomly loses WiFi Calling. To solve this, I've been keeping my phone airplane mode with WiFi on and haven't experienced any type of disruption of service. Calls sounds great.
Click to expand...
Click to collapse
Worked like a charm on Romania's Orange network. Both VoLTE and VoWiFi seem to work well.
Thank you for the tip.
Ulver said:
On a side note, since you're on T-Mobile US, are you getting LTE+? I was showing LTE+ on my Mix 2S and Mi 8, but doesn't show up on my Mi 9.
Click to expand...
Click to collapse
I don't know if it helps, but in Romania on Orange I have 4G+ almost all the time while on my old Oneplus 5T I didn't...
Volte Orange Romania
Hello , i have activated both, i have no options in settings.
bogdanpop74 said:
Hello , i have activated both, i have no options in settings.
Click to expand...
Click to collapse
It's a carrier specific option. So go to phone-> settings-> Sim cards &.....-> Orange and should be the last two options.
Hmm...I've activated both too but only get the volte option, no wifi calling toggle switch. Tmobile USA running no root, stock miui 10.2.3. Did anyone on tmobile USA get wifi calling to work? Also, if you did, does it also activate wifi texting?
Update: guessing the volte doesn't require a restart but wifi calling requires a restart. To those who run into the same prob as me.
Ídem here, no volte options, my carrier support it and works on a s7 edge, any ideas?
Envoyé de mon MI 9 en utilisant Tapatalk
mNiosu said:
It's a carrier specific option. So go to phone-> settings-> Sim cards &.....-> Orange and should be the last two options.
Click to expand...
Click to collapse
After update to Miui 10.2..24.0 options for VoLTE and VoWIFI appears in menu and i can activate both.
unlike you, since the last update 10.2.24.0 I lost the option volte/vowifi, when I try to reactivate it, the phone tell me it's enabled for the SIM 2 but I have no sim two,
if i swap the sim card it tell me activated for the sim 1 ...
Same here, after the new update 10.2.24.0 i have the same message like you.
ricjuh said:
Also works in Netherlands with Vodafone
Click to expand...
Click to collapse
I activated volte and wifi calling, but when I go on flight mode and activate wifi, wifi calling is not working and there is no sign in status bar too. I am Vodafone Germany and on my Samsung it was working.
How did you get it working?
Sent from my [device_name] using XDA-Developers Legacy app
putti71 said:
I activated volte and wifi calling, but when I go on flight mode and activate wifi, wifi calling is not working and there is no sign in status bar too. I am Vodafone Germany and on my Samsung it was working.
How did you get it working?
Sent from my [device_name] using XDA-Developers Legacy app
Click to expand...
Click to collapse
Did a quick test on mine (T-Mobile/Germany) and it's working. I just used the dial-codes and enabled wifi calling. Had to change the preferred connection type to wifi-prio though - wasn''t working with cellular-prio and flight mode before.
It works!
lightcao said:
Just wanted to share my experience with WiFi Calling. I am in the US on T-Mobile and WiFi calling has been working for me surprisingly. VoLTE has also been working wonderfully. I've tested this on a Global Mi 9 running Stock and the Xiaomi.eu rom.
Enter these codes into the Dialer to enable the options in Settings. (Settings < SIM Cards & mobile networks < Sim Card Settings < VoLTE Enabled/Make Calls using WLAN)
VoLTE *#*#86583#*#*
VoWIFI *#*#869434#*#*
Things should work after you enable the two options. This depends on whether or not your carrier supports it and your e911 address set (US only?).
Some issues you might run into is that the option for Network Preference is greyed out and you will unable to change that option. I've had some success if you disable it and re-enable it and click on that option really fast, it will go through. Another thing is that WiFi calling might glitch out if you have cellular on. It just randomly loses WiFi Calling. To solve this, I've been keeping my phone airplane mode with WiFi on and haven't experienced any type of disruption of service. Calls sounds great.
Click to expand...
Click to collapse
Awesome it said not supported by carrier on Xiaomi.eu ROM but now it is working
VoLTE *#*#86583#*#*
VoWIFI *#*#869434#*#*
Click to expand...
Click to collapse
These codes worked good on my brand new & stock MI9 Global.
Sadly Virgin UK has not using them.
Thanks
These codes Wlworks well to enable volte. But there isnt Amy volte symbol in my phone. So os volte working in my mi9? My s7 always had a symbol for volte.
gui.aguiar said:
These codes Wlworks well to enable volte. But there isnt Amy volte symbol in my phone. So os volte working in my mi9? My s7 always had a symbol for volte.
Click to expand...
Click to collapse
Download a signal app from the Play Store and make a phone call. If you still have 4G when making the call Volte is working. If the signal drops to 3G after the call connects Volte is not working.
jhs39 said:
Download a signal app from the Play Store and make a phone call. If you still have 4G when making the call Volte is working. If the signal drops to 3G after the call connects Volte is not working.
Click to expand...
Click to collapse
I did It and volte is not working...
I have a Mi 9 global version running the latest stable global Room. I'm trying to turn VOLTE on, but I'm nota being sucessfully.
I've tried enable It via MCC code (*#*#4636#*#*) but It doesnt work. The option to enable VOLTE os greyed out.
How can I enable It? My old s7 suport VOLTE with the same sim card.
Related
So, my carrier suggests for themselves it's a proprietary solution they bake into their phone roms, and may well be. However, they've recently liberalized registration for this service which suggests they may be implementing broader access for devices.
Anyhow, I was just wondering - if we are to operate under the assumption that wifi calling works on my carrier and compatibility doesn't get in the way.... how would I actually activate it and verify that it is active? Ideally on this ROM, but if it's not too deviant, any process would be appreciated.
Thank you for any assistance.
I am using official RR oreo and wifi calling works perfectly fine with my carrier.
Heyyo! Your best option for testing it is to try out AEX or Pixel Experience as ShivaTehaPeddi is the guru of VoLTE, VoWifi and ViLTE and such. :good:
I'm unsure if he has the latest Canadian APN settings but my unofficial LineageOS 15.1 builds do include them.
I'm with Fido and when I tried it with Koodo Mobile both carriers I get IMS registration failed.
To check this? Enable VoLTE and VoWifi in your settings under mobile data.
Then go I to your dialer app and dial...
*#*#4636#*#*
It sometimes takes a few minutes to open if your phone is freshly booted.
Then in the menu select IMS status and hope for the best.
arpit1234567 said:
I am using official RR oreo and wifi calling works perfectly fine with my carrier.
Click to expand...
Click to collapse
With respect, that addressed literally nothing I asked.
I'm not on your carrier. I'm not asking if voWifi works generally. Etc. etc.
ThE_MarD said:
Heyyo! Your best option for testing it is to try out AEX or Pixel Experience as ShivaTehaPeddi is the guru of VoLTE, VoWifi and ViLTE and such. :good:
I'm unsure if he has the latest Canadian APN settings but my unofficial LineageOS 15.1 builds do include them.
I'm with Fido and when I tried it with Koodo Mobile both carriers I get IMS registration failed.
To check this? Enable VoLTE and VoWifi in your settings under mobile data.
Then go I to your dialer app and dial...
*#*#4636#*#*
It sometimes takes a few minutes to open if your phone is freshly booted.
Then in the menu select IMS status and hope for the best.
Click to expand...
Click to collapse
Sorry to only address this now, but I tried that and I just get a robot saying (with a seemingly Chinese accent, no idea if that's related or not): "Please enter 6 digit password for ... ip something .. account then press pound."
Any thoughts?
So i got my Mi 8 Pro yesterday (Global Version). The one feature I cannot seem to activate is Wifi Calling, I have done both the *#*#86583#*#* (voLTE) and *#*#869434#*#* (voWIFI), both options are enabled in *#*#4636#*#* and when i go into my sim settings both VoLTE and Wifi Calling are enabled
voLTE shows the symbol in my task bar however wifi calling never seems to enable? Is there some other setting I am missing or do I need to get EE to disable and re-enable it on my account since I've swapped phones? It's vital for me as I work in a lot of places without cell reception so i rely on wifi calling.
Any help is appreciated
Neo1607 said:
So i got my Mi 8 Pro yesterday (Global Version). The one feature I cannot seem to activate is Wifi Calling, I have done both the *#*#86583#*#* (voLTE) and *#*#869434#*#* (voWIFI), both options are enabled in *#*#4636#*#* and when i go into my sim settings both VoLTE and Wifi Calling are enabled
voLTE shows the symbol in my task bar however wifi calling never seems to enable? Is there some other setting I am missing or do I need to get EE to disable and re-enable it on my account since I've swapped phones? It's vital for me as I work in a lot of places without cell reception so i rely on wifi calling.
Any help is appreciated
Click to expand...
Click to collapse
Hello, my friend is also like you, he is the development version of WiFi can not be used but the stable version of the MIUI system can be used. You can try to re-wire the stable version of the MIUI system, I wish you good luck.
I really need WiFi Calling in order to reasonably use this phone for calls from my house due to a poor Network signal. There is no Wifi Calling option in Calls -> Settings or in Settings -> Network & internet -> Mobile network anywhere. Also when I do *#*#4636#*#* and go into Phone information Wifi Calling Provisioned option is grayed out.
Nope. Last time I saw wifi calling available was on the XZP. Wasn't an option for the XZ3, and still not an option for the Xperia 1. Try giving tmobile a call or maybe sony support and ask if they can add wifi calling support.
reiriop said:
I really need WiFi Calling in order to reasonably use this phone for calls from my house due to a poor Network signal. There is no Wifi Calling option in Calls -> Settings or in Settings -> Network & internet -> Mobile network anywhere. Also when I do *#*#4636#*#* and go into Phone information Wifi Calling Provisioned option is grayed out.
Click to expand...
Click to collapse
Option is here for me. Can you not flash a non branded firmware?
Mackay53 said:
Option is here for me. Can you not flash a non branded firmware?
Click to expand...
Click to collapse
Which frimeware is that ? Is that US unbranded
Nope, no wifi calling for me. I originally had the J9110 model (international dual sim, hong kong) but i recently flashed it with the US firmware. No dice, unfortunately. But since changing to the US firmware, I now get VoLTE and group message in Android Messages. It's a start.
Ya VoLTE is working fine and appears as provisioned in the hidden menu. So it seems like I will have to do something similar to what I did on the XZ Premium in order to get WiFi Calling...but I will wait until there is a DRM backup process.
reiriop said:
Ya VoLTE is working fine and appears as provisioned in the hidden menu. So it seems like I will have to do something similar to what I did on the XZ Premium in order to get WiFi Calling...but I will wait until there is a DRM backup process.
Click to expand...
Click to collapse
I see the same thing as you. How did you do it on the xz premium?
I had to root it and flash a zip that someone made for it, it might be possible to use the same zip but I'm not going to root mine until there is a DRM backup method. I barely every talk on the phone without LTE service so it's more so just really annoying not having WiFi Calling. I think a bunch of people were using the same zip for the 2017/2018 xperia phones to get it working.
I have XZ premium and XZ1 and wifi calling option is displayed when I use the Jio sim but not displayed when using Airtel sim (using Airtel broadband), so our phones do have wifi calling facility but working only with Jio sim, although Sony is not shown in the compatible phones list. I am in India.
That also stresses me out on My Xperia 5. Don't know If You talked about My Zips for VoLTE and the other Features but i didn't get it to work actually on Android 10. Possible that i just don't have the right Firmware atm (Customized EU / My Devices Firmware isn't Out yet), so i'm using Custom UK Firmware but that should also work... I'm a bit confused so i switched to GSIs which Made it even worse... Looks like we should start making Custom Vendors for our Xperias since the Methods changed over Android 7-8-9-10
Can you flash the dual sim model to work with a single sim firmware and does Wi-fi Calling Work later?
yes, that's what i did with my xz3. volte works with tmobile, but not att.
Hi, I am getting desperate now trying to get VoWifi/wifi calling to work on my mate 20 pro.
My wife has the same phone, and same Carrier (even same plan)
The carrier is called Talkmore which is an daughter company of Telenor. I'm living in Norway btw.
The thing is that on my wifes phone, the carrier says Telenor ViWifi in the top corner, but on mine it says Talkmore HD.
We did have different apn's also, but I changed it on mine to the same as my wifes phone, but still it's then same.
And yes, I have turned on Wifi calling in the settings
I have talked to Talkmore, and everything is okey on their part, and you know there is not much tech help to get from carrier employees.
Does anyone have any tips that I can try. It would be appreciated.
Thanks in advance!
Hi,
With this app https://play.google.com/store/apps/details?id=by4a.setedit22
Check in 'GLOBAL' tabs of both devices the line starting by
wfc_ims_*
Any differences beetween the 2 devices ?
oslo83 said:
Hi,
With this app https://play.google.com/store/apps/details?id=by4a.setedit22
Check in 'GLOBAL' tabs of both devices the line starting by
wfc_ims_*
Any differences beetween the 2 devices ?
Click to expand...
Click to collapse
There is a difference on mine and hers. The first photo is mine, the second one hers.
Some carrier are calling Volte and/or Vowifi HD. Maybe yours is one of them.
Disable Vowifi, Choose airplane mode, then enable wifi, then enable vowifi.
Does HD icon shows while still on airplane mode with wifi and vowifi on ? -If so, your carrier use the HD icon for vowifi.
Your carrier is actually using HD icon for Volte.
oslo83 said:
Some carrier are calling Volte and/or Vowifi HD. Maybe yours is one of them.
Disable Vowifi, Choose airplane mode, then enable wifi, then enable vowifi.
Does HD icon shows while still on airplane mode with wifi and vowifi on ? -If so, your carrier use the HD icon for vowifi.
Your carrier is actually using HD icon for Volte.
Click to expand...
Click to collapse
That didn't work.
What happens if I remove the extra stting that I have on my phone? Maybe it's worth a try?
I would try to add on yours, the key:
wfc_ims_enabled
with value set to
1
wfc_ims_mode_X values are:
3 for Mobile prefered over Vowifi
2 for Vowifi prefered over Volte & Mobile
1 for Volte ptefered over vowifi
_X is :
_0 for SIM1 and
_1 for SIM2
oslo83 said:
I would try to add on yours, the key:
wfc_ims_enabled
with value set to
1
wfc_ims_mode_X values are:
3 for Mobile prefered over Vowifi
2 for Vowifi prefered over Volte & Mobile
1 for Volte ptefered over vowifi
_X is :
_0 for SIM1 and
_1 for SIM2
Click to expand...
Click to collapse
Hi. Sorry for the late reply. Been busy the last days.
I tried your suggestion which did not work. I also messed around a bit, including deleting the string like I said, but no luck with that either
Hi all,
I hope this is the right forum for this question and, if not, I apologise.
I live in Australia. My telephone provider, Boost Mobile, provides VoLTE and VoWIFI capabilities. On my previous Umidigi F1 smartphone I was able to use both, but when I moved the same SIM card on my Mi 10 Pro I couldn't find any settings, although I know the Mi 10 Pro has VoLTE and VoWIFI capabilities.
I cannot see anything where to activate them, no settings. I tried these codes as recommended in some posts on here, but they seem to do nothing. As soon as I press the star and the end of each code, they simply disappear and no message is visualised on the screen, neither any option appears in the SIM settings.
To unlock VoLTE: open your phone app and dial *#*#86583#*#*
To unlock VoWifi: open your phone app and dial *#*#869434#*#*
I have a MIUI global 11.0.4.0 (QJAMIXM)
Do you any suggestion? Thank you in advance!
Cheers,
G.
detonazione said:
Hi all,
I hope this is the right forum for this question and, if not, I apologise.
I live in Australia. My telephone provider, Boost Mobile, provides VoLTE and VoWIFI capabilities. On my previous Umidigi F1 smartphone I was able to use both, but when I moved the same SIM card on my Mi 10 Pro I couldn't find any settings, although I know the Mi 10 Pro has VoLTE and VoWIFI capabilities.
I cannot see anything where to activate them, no settings. I tried these codes as recommended in some posts on here, but they seem to do nothing. As soon as I press the star and the end of each code, they simply disappear and no message is visualised on the screen, neither any option appears in the SIM settings.
To unlock VoLTE: open your phone app and dial *#*#86583#*#*
To unlock VoWifi: open your phone app and dial *#*#869434#*#*
I have a MIUI global 11.0.4.0 (QJAMIXM)
Do you any suggestion? Thank you in advance!
Cheers,
G.
Click to expand...
Click to collapse
have u try this code
*#*#4636#*#*
-fluffy- said:
have u try this code
*#*#4636#*#*
Click to expand...
Click to collapse
Thank you. Unfortunately nothing happened after I wrote that code. I didn't get any message and I couldn't see the options like in the screenshot you sent.
detonazione said:
Thank you. Unfortunately nothing happened after I wrote that code. I didn't get any message and I couldn't see the options like in the screenshot you sent.
Click to expand...
Click to collapse
have try power off the phone then power it on again an wen it starts enter the code
I did as you suggested but, unfortunately, nothing happened even this time. I wonder if these options have been disabled on purpose
detonazione said:
I did as you suggested but, unfortunately, nothing happened even this time. I wonder if these options have been disabled on purpose
Click to expand...
Click to collapse
what miui are u on
---------- Post added at 09:15 AM ---------- Previous post was at 09:14 AM ----------
btw have u try clear all data fore phone app
-fluffy- said:
what miui are u on
btw have u try clear all data fore phone app
Click to expand...
Click to collapse
Thank you for your help @fluffy, I'm on MIUI global 11.0.4.0 (QJAMIXM)
This phone is new, I have it from a couple of weeks.
I also tried to clear storage and cache for the phone app, but still nothing happens
@fluffy, I installed an app called "MIUI Quick Settings" and I managed to see the settings like in the screenshot you sent me. The parts about VoLTE and VoWifi are greyed out and I cannot change them.
detonazione said:
@fluffy, I installed an app called "MIUI Quick Settings" and I managed to see the settings like in the screenshot you sent me. The parts about VoLTE and VoWifi are greyed out and I cannot change them.
Click to expand...
Click to collapse
try an see if u cant actived them now with the codes
---------- Post added at 11:34 AM ---------- Previous post was at 11:25 AM ----------
i have just testet *#*#4636#*#*
an it does the same as urs do
but try go into settings network
simcard settings an see if they aint there
they are in my phone even that i cant actived them in that code
---------- Post added at 11:36 AM ---------- Previous post was at 11:34 AM ----------
-fluffy- said:
try an see if u cant actived them now with the codes
---------- Post added at 11:34 AM ---------- Previous post was at 11:25 AM ----------
i have just testet *#*#4636#*#*
an it does the same as urs do
but try go into settings network
simcard settings an see if they aint there
they are in my phone even that i cant actived them in that code
Click to expand...
Click to collapse
an u know that wen u enter the volte code it will disapere with in a sec
there is only coming a short notise that it is on
detonazione said:
@fluffy, I installed an app called "MIUI Quick Settings" and I managed to see the settings like in the screenshot you sent me. The parts about VoLTE and VoWifi are greyed out and I cannot change them.
Click to expand...
Click to collapse
Maybe try with another dialer? I know Google dialer didn't worked for me when I flashed global rom
I activated using pdc , need Root.
criszz said:
I activated using pdc , need Root.
Click to expand...
Click to collapse
How?
Enviado desde mi Mi 10 mediante Tapatalk
Has anyone been able to successfully activate vowifi with the global Mi 10 Pro?
I can disable WiFi carrier check using *#*#869434#*#* which gave me the " Make calls using WiFi" option in mobile network settings. Although the option is checked, it doesn't seem to be working using a Telstra SIM (which has WiFi calling perfectly with an iPhone 8) .
Dialling *#*#4636#*#* reveals that WiFi calling provisioned is still disabled and greyed out.
Any ideas?
Krisbo said:
Has anyone been able to successfully activate vowifi with the global Mi 10 Pro?
I can disable WiFi carrier check using *#*#869434#*#* which gave me the " Make calls using WiFi" option in mobile network settings. Although the option is checked, it doesn't seem to be working using a Telstra SIM (which has WiFi calling perfectly with an iPhone 8) .
Dialling *#*#4636#*#* reveals that WiFi calling provisioned is still disabled and greyed out.
Any ideas?
Click to expand...
Click to collapse
Me too, i can't see volte icon too, never seen, instead it works with my operator on every other phone i have
i know this is an old thread but wanted to say thanks, i have a mi 10 ultra and im on Telstra (Australian Network) using the 2 codes in the OP both came up with a quick popup after entering saying "disabled volte/wifi carrier check" and now in the sim options both the volte and vowifi options show up and when enabling them the vowifi icon shows in the top so thanks!! (i chose to prefer wifi network over mobile networks in the vowifi options) EMUI version in screenshot.
When I use the codes in the OP I also get voWIFI and voLTE in the status bar and they work, but I lose caller ID so I cant see whos calling me.
I m in the UK on Virgin, I moved from Vodafone a few days ago to Virgin, on Vodafone both voWIFI and voLTE worked, but I didnt get the voWIFI and voLTE signs in the status bar, I also got caller ID.
The weird thing is that Virgin is a MVNO that now uses Vodafones network.
WIFI calling, video calling and voLTE are still greyed out in MUI settings even though I can now get them, all very strange.
I think you are all misunderstanding the technology.
There is a few dependencies. Signal availability, Signal strength and MOST importantly the other caller MUST be the same and on the the same network provider.
Now, I can't speak for other countries mainly because I don't live there, but here in the UK VOLTE will be either "4G" or "4G+" where the signal bars are displayed. By now the majority of the UK will be "4G" which technically IS VOLTE because the technology is a data carrier with a voice protocol strapped to it. This is why the provider must be the same for BOTH callers or it will fallback to 3g for the call for BOTH callers.
4G+ is LTE-A (LTE ADVANCED) is a dual band version of 4G which will attempt to use one band for keeping data alive and the other band for VOLTE. Again, this is dependent on the same factors as 4G with the same fallback rules.
5G is technically 'the standardisation' of all providers so the signal doesn't fall back.
I am in the UK. Stock Mi10 5G on a Giffgaff (O2) simcard. I can get all of them.
I think you have missed the point I was making - the same phone on Vodafone voLTE and voWIFI works, but I change to an MVNO that uses the same Vodafone network, I use the same phone, but suddenly neither works. There is clearly something on the carrier side that they do to enable or disable registering IMS, my previous Le Max 2 was voLTE and voWIFI compatible yet I could never get it to work on Vodafone even after having a massive dispute with them about it, I concluded then that there is somehting their end stopping it from working, my expereience above seems to confirm this. Quite why they designed voLTE and WIFI like this I dont know - they should just work just as 2G and 3G calling do.
I have never heard that the caller must also be on the same network, that does not sound right to me and indeed when was on Vodafone I could call non Vodafone users and still get voLTE.
Because Vodafone aren't obliged to share their full network with other providers like vermin media. Although you think they are one in the same they aren't. Vermin rent from Vodafone so it is a sub system. Why would Vodafone give anyone else Admin over their network?
Regardless of whether you think you have full 4g at both ends if the other caller doesn't for whatever reason you get the best that they can do and nothing more. There is no upscaling. That's why you need to both be on the same network/provider.