Another T-Mobile VoLTE question

[Bill31]

I'm really trying to make sense of this issue of VoLTE in the US but I just can't wrap my head around it. 

I have a Umidigi 5G phone that is not on the PM whitelist. I go to the T-Mobile webpage and enter the IMEI of my phone and they say that it can use all the features of their network, including VoLTE.

Now, from what I've read on different posts in this Community, what seems to be agreed upon is: if I try to make a call on the T-Mobile network they will not allow the use of VoLTE even my phone is VoLTE compatible on their network and if PM has VoLTE, just because it isn't on the PM whitelist.

I just chatted with the PM computer, asked the question and got this reply:

"Here is the most relevant information I found for you. Hope this helps! VoLTE will work in the US on the T-Mobile network if the device is VoLTE compatible and not specifically on the Public Mobile whitelist.
As long as the device is VoLTE-capable, it should work on the T-Mobile network for VoLTE calls."

Have I misinterpreted all the posts here?

[Bill31]

It's really hard to get confirmation of all this from the actual network operators, so I decided to do what I normally do when I'm stuck ... give ChatGPT a try. It's not perfect, or always right, but it can do a lot of the legwork to point me in the right direction. Here's ChatGPT's reply:

The statement that "all your mobile activity is routed back through the Public Mobile network in Canada, even when roaming in the U.S." is partially true but can be misleading in the context of how VoLTE works during roaming.

How Roaming Typically Works:

1. Voice and Data Roaming: When you roam in the U.S. on T-Mobile, your phone connects to T-Mobile’s towers. For most functions like calls, texts, and data, the T-Mobile network handles the connection and then routes it back to Public Mobile in Canada for billing and service management.

2. VoLTE and Network Control: While it's true that Public Mobile controls your account settings, the actual voice call quality and whether VoLTE works are determined by the network you are roaming on (in this case, T-Mobile). For VoLTE, T-Mobile must recognize your device as compatible with their VoLTE system. Once that’s confirmed, the call setup and voice transmission happen over T-Mobile’s VoLTE infrastructure, not directly through Public Mobile’s Canadian infrastructure.

3. Routing Calls: While data from roaming might still route back through Public Mobile for billing or monitoring purposes, the actual VoLTE capability is dependent on the network you’re currently using (T-Mobile). Public Mobile doesn’t typically block VoLTE access on roaming networks if the roaming partner allows it.

Conclusion:

In practice, if your phone is compatible with T-Mobile’s VoLTE service, it should work for making VoLTE calls while roaming in the U.S., even if Public Mobile does some back-end routing. The primary factor is T-Mobile's acceptance of your device for VoLTE.

It’s understandable why there might be confusion. The key point is that when roaming, the local network’s capabilities (T-Mobile’s VoLTE) take precedence over Public Mobile’s restrictions regarding VoLTE compatibility. 

[will13am]

@Bill31 , network access is controlled by Public Mobile even when roaming in the US.  All your mobile activity is routed back through the Public Mobile network in Canada.  So the cork in the bottle is the Public Mobile VoLTE whitelist.  It determines how calls are transacted.  If you were to subscribe to a T-Mobile service in the US, then your phone will work for calls.  I too have a Umidigi phone that does not get VoLTE.  I have advocated for changes to the VoLTE whitelist but there is no appetite to do so.  

[softech]

@Bill31 

with a non VoLTE whitelisted phone, you will rely on T-Mobile's 2G network for voice.  However, T-Mobile will be shutting down the 2G network soon as well.  

So, what I recommend is to use VoIP app TextNow to make and receive calls using the app with another 10 digits number assigned by the app  The app will works as long as you have data or Wifi when you are in US

[Bill31]

Thanks for your reply.

The question I have pertains to your last sentence, which seems to be what nearly everyone else is saying. It is believed that, as yous say "non-VoLTE whitelisted devices on PM's network more than likely will not be able to work for calls". Yet, PM says "VoLTE will work in the US on the T-Mobile network if the device is VoLTE compatible and not specifically on the Public Mobile whitelist.".

Thanks again for taking the time to reply. 

[eddieO]

Hi @Bill31, So we are in the same situation with my wife's phone, it's VoLTE capable but not on the PM whitelist. While in Florida a few months ago my wife was able to send/receive text, and use data on both T-Mobile and AT&T. When it came to calling, it would not work for her at all on AT&T, she had to manually connect to T-Mobile and then she was able to make and receive calls. Verizon wouldn't even work for any of the service although we're hearing more and more customers say that it worked for them, maybe we were in the beginning of the rollout for that. Honestly, this wasn't an issue for us at all as there are so many alternatives, she was able to make video calls through WhatsApp that worked flawlessly and you can make audio calls (no video) through WhatsApp but there are other apps you can use as well like Facebook's Messenger etc

T-Mobile is apparently looking to shut down their 2G service in the U.S. very soon (was supposed to happen on April 2, 2024 but was postponed), when this happens non-VoLTE whitelisted devices on PM's network more than likely will not be able to work for calls