Global (non-US) Android phones don't work on AT&T in the US

I don't know what list you're looking at, but the one I see has a lot of non-AT&T unlocked models. But even then, there is still a disclaimer that such phones still aren't guaranteed to work.

BTW, the unlocked US model numbers are not the same as unlocked global variants. And, of course most global variants won't work as they aren't intended to be sold in the US.

The list I'm looking at:

https://www.att.com/idpassets/images/support/pdf/Devices-Working-on-ATT-Network.pdf

That's not the unlocked phone list... 

Service capabilities of unlocked devices https://www.att.com/ecms/dam/att/consumer/help/pdf/Service-Capabilities-Unlocked-Devices-ATT-Network.pdf

You will find that there are many Brands which are excluded. They are excluded by their own choice. Manufacturers had to submit their phones for testing, and be willing to accept AT&T software to allow their phone to work on AT&T with their voice over LTE coding.

Huawei and ZTE unlocked are still banned. 

Thanks but the list is mostly the same as in the file I posted.

You asked, "why".  The answer to that was in my second paragraph. The manufacturers choice... 

Hello cluelessinsd, Learn why your previously working device may have stopped working this February and how to determine if it's compatible.

We would like to thank our Aces for responding. If you have a 3G device, please note, it will no longer work on the AT&T Network. If you have a 4G device, it may not be compatible and not work depending on where it was purchased and the model #. For example, the Galaxy S20 models G981U and G981U1 will work on the AT&T network, but the Galaxy S20 models G981F, G981N, and G981O will NOT work. You'll find a full list of compatible devices. This is because they have different hardware that is not compatible with AT&T’s network (HD Voice, VoLTE compatible). 

If you purchased an unlocked device from another retailer, please note, they are not optimized to work on AT&T’s network. This is important to remember when purchasing a non-branded, unlocked device and why you see different model numbers.  

Let us know if this helps.

Thank you for visiting AT&T Community Forums!

Carlton, AT&T Community Specialist 

Thanks ATTHelp. But AT&T's deliberate decision to exclude most unlocked devices is just not right. They will work fine on 4G. Why not let the customer decide? It's not AT&T's responsibility.

It's AT&T's network.  It's their system that phones have to run on.  They have to right to pick and choose what's allowed to connect.  You may not like it, but would you allow just any person to wander in your home just because they have two legs and can walk like you and your friends?  I assume you might want to be a bit selective in that case.  AT&T is too.  That's just the way it is, and it doesn't seem to have been hurting AT&T's bottom line.

You can always try T-Mobile.  They tend to be more open to a wider range of unlocked devices.

Verizon? Probably even more restrictive than AT&T.

Actually I agree with Clue...AT & T is a network provider they are not a phone manufacturer.   By only accepting a small number of phones on their network they have created an oligopoly.  Unless you choose Google, Samsung, or Apple you can't really get a flagship phone and that is wrong.  There are many brands out there - many Chinese brands such as Oppo and Vivo even Japanese brands like Sharp where they won't let them on their network claiming they won't work yet we know this is a lie because you can purchase a mvno sim card and it will work fine.  Let's face it every phone in the world is produced in China.  Even when you have a T-mobile sim in a phone and T-mobile supports it and you roam on AT & T (and T-mobile has a roaming agreement) AT & T won't let it operate.  It's ridiculous.  And I get it - I am more of an enthusiast but that represents a fairly large number of people in the US that can't use AT & T because they refuse to support global devices.  Ultimately network providers should be just that - network providers.  They shouldn't have say over what devices can work on their network that should be up to the FCC.  If a device is FCC approved - take the Oppo Find x2 pro global version then it should work on any network in the US and it is user beware - the user needs to know what frequency bands their phone has what the network supports and can make an informed decision from there.  AT & T's claim about their version of volte is different - first of all volte is a standard and the HD voice software could easily be sent via a provisioning text when a sim card is inserted.  Xiaomi phones - all you need to do is enter a code and you will get either volte or hd voice dependent on what network you are on and they are interchangeable.  But I am firm believer that if a phone is FCC approved then the network providers should not be able to police the devices otherwise as said they create an oligopoly.  Also banning ZTE and Huawei devices prior to the ban is an issue when those devices still have google services and still get updates and should by all definitions still work fine.  That applies more to Huawei (phones like the p30 pro) then ZTE as Red Magic phones are sold in the US and I believe should work on all gsm networks.   

@vpoppo1 

I believe should work on all gsm networks.   

Did you know there are no more GSM networks? Except for whatever 2G network that T-Mobile has yet to shut off.   AT&T is not a GSM network anymore. Minimum functionality requires LTE.  Verizon is not a CDMA network anymore. They have no more CDMA. Verizon is also a minimum LTE network.

As stated before, it is up to the manufacturer to get their phone tested for compatibility, and then it can make the list. There are far more than three brands.  While they are not all flagship, it does offer choice.

Alcatel, apple, asus, blu, cat, essential, google, kyocera, lg, microsoft, motorola, Nokia, pepperl+ fuchs, punkt, Raz, one plus, samsung, Sony, tcl, schok, sonic, Terra cube, ZTE

23 brands

9 offer what I would consider a flagship quality phone. Many of them multiple flagship quality phones.

If you're not happy with it complain to the manufacturer of your choice. FYI  OnePlus is a subsidiary of OPPO.  

Huawei and ZTE were banned.  That's their own doing. The only Huawei or ZTE phones that will work in the United States are ones that were built and sold directly by a manufacturer. 

AT & T's claim about their version of volte is different - first of all volte is a standard and the HD voice software could easily be sent via a provisioning text when a sim card is inserted. 

It could be, if the manufacturer would submit the phone for testing. But they won't. 

If you want to use something that's not on AT&t's acceptable list, then switch to T-Mobile. T-Mobile is not an American company. It's primary owner is a German Telecom.