256QAM, you would have (T-Mobile has 256QAM and 4x4 MIMO). But you're correct about Carrier Aggregation being affected.
The issue is that most Android phones' IMS profiles are baked into the firmware for the carrier that they're sold on. Unlike the iPhone, most Android phones are not meant to be "universal". However, if we ignore other brands and focus on Samsung Unlocked devices, you're right. Just like with our unlocked Samsung phones, it would require an update from Samsung to add the profiles to the AT&T CSC. Clearly they were not included as a business deal between them an AT&T, because there is literally no other explanation. With 3G going away they have no choice but to enable VoLTE.
If you check my reddit thread here, you can see an AT&T rep chimed in to say they'd have it working by the end of the way.
However, there's nothing stopping Samsung from including the profiles now. This is 100% a business decision between them an AT&T. Even ***VERIZON*** allows VoLTE and Wifi Calling on Unlocked devices. And they used to be the harshest. Google and AT&T talked about the Pixels, but here's even more BS. Pixel 2 only gets VoLTE and the 3 gets VoLTE and Wifi Calling.
... View more
Sorry, to correct myself it works. You're gonna like this though:
How I got this:
I disabled the "AutoPreconfig" service that is responsible for reconfiguring the device based on carrier SIM card. I had my T-Mobile SIM in the device. Disabled the service. Popped in the inactive AT&T SIM I have. What do you know? The profiles load (though you have to enable them manually in the app with the 3-dot menu). I cannot test if they work because I don't have active AT&T service, and on top of that you need to lie about your IMEI # to AT&T to get them to even enable it on their side.
Essentially I put the device into Unlocked-T-Mobile mode, and prevented it from rebooting to go into Unlocked-AT&T mode. The IMS Settings app was able to load an IMS Profile for AT&T with the AT&T SIM in the phone in Unlocked-T-Mobile mode. There is an option to manually register/turn on the IMS profile, but you need to have AT&T service and have AT&T enable VoLTE/Wifi Calling on their end by giving them an iPhone IMEI or AT&T device IMEI.
The downside to this is you get slightly slower AT&T service (you may or may not notice) because T-Mobile doesn't use LTE Bands 29 and 30 (they are enabled and disabled in software). So the phone won't use Bands 29 and 30 in this mode.
... View more
Interesting -- On the Note 9 Unlocked, the menu doesn't come up with an AT&T SIM (I'm on T-Mobile now, but would like to go back to AT&T). If you go into the IMS Profiles section of the app, do any profiles actually come up in the list?
... View more
I have extensive knowledge about this. The Samsung IMS Framework is used across all US carriers. I left AT&T for T-Mobile over this (had an unlocked S8+, now Unlocked Note 9). With T-Mobile or Verizon, an IMS profile is registered and those come up as "True". However, on the AT&T CSC on the Unlocked models, Samsung purposely does not provide any IMS profiles. There is no other reason than some kind of deal with AT&T. However, this is a $1,000+ device, and 3G is practically useless in major cities. In addition to this, it's not advertised that VoLTE and Wifi Calling (which are basic features, not luxuries) don't work with AT&T. AT&T is killing off 3G (and like I said, it doesn't even work here in NYC), so if you don't do anything, we cannot make calls or text and our phones will become expensive tablets.
You can flash the AT&T firmware, but that defeats the purpose of using the Unlocked model/ROM. That also won't fix things fully; there are additional hoops involving lying to AT&T about your IMEI #.
Samsung staff - We deserve an explanation and a fix here. S7, S8, S9, Note 8, Note 9, S10.
@RedDragon -- Can you tell me how you got into the IMS Settings menu with an AT&T SIM inserted? On my Note 9 Unlocked it doesn't work with an AT&T SIM inserted.
... View more