Why not support the device from Xiaomi, the 3rd largest global cellphone maker?

Hello @jmf0690, we're here to help with information about the 3G shutdown and compatible devices that will work on the AT&T network.

Since we shut down the 3G network, there won't be data or voice service for devices that don’t have at least have 4G capabilities. This means that while some device features might still work, you won’t be able to access our network unless you upgrade to a newer device.

•  It’s important to check the device model numbers to make sure it’s still supported since the 3G network shutdown. This includes iPads, tablets, and wearables. Check out our list of supported devices.
• Once you know your device still works, you may need to restart your device or check the VoLTE or LTE status. 
• Don’t see your phone make and model on the list? That means it may not work anymore. You may need to swap or upgrade to a new one.

Your phone will work if the HD Voice feature is turned on. If you can’t make or receive calls, or you’re having trouble accessing data, check the VoLTE or LTE status of your phone. Here’s how:

• iPhone 7 and above: Go to Settings, then General, and lastly Software update. Select Download and install to update to the most current software version.
• iPhone 6: Go to Settings, then Cellular, and then Cellular data options. Choose Enable LTE then select Voice and Data and turn on LTE.
• Android: Go to Settings and then Connection. Choose Mobile networks and then Enhanced LTE services and select On.

Let us know if you have any questions. Thank you for contacting AT&T Community Forums.

Alasani, AT&T Community Specialist 

Because they (Xiaomi) didn't submit phone models for testing to show it capable of voice calls over the LTE network 

Since this isn't a phone that targets the US, and wasn't intended to even be sold in the US market, that probably explains why Xiaomi didn't pay to get it certified for ATT.  ATT has taken the current position that phones have to be certified for their network before they will allow them to be used.

That's like saying; unless you buy only Chevron gas, your car will not run. U.S. home of the free.

@jmf0690 That's like saying; unless you buy only Chevron gas, your car will not run. U.S. home of the free

No, it’s like saying if you don’t follow EPA, state, and other federal guidelines you can’t sell you gasoline in the US.  

• https://www.epa.gov/gasoline-standards/federal-gasoline-regulations
• https://www.ecfr.gov/current/title-40/chapter-I/subchapter-U/part-1090
• https://www.ftc.gov/business-guidance/resources/complying-ftc-fuel-rating-rule

The car you want to use that gasoline also requires that a bunch of rules to be followed, including being registered, and needs a license plate to be driven on the roads. 

Don’t forget about the driver, they need to take a test and have their own license…

That's like saying; unless you buy only Chevron gas, your car will not run. U.S. home of the free.

Im choosing a simple analogy...

AT&T is Diesel and your car only takes regular gas.

Analogies are fun, but the fact is you're using a phone that's not made to run in the United States by a manufacturer that never intended for its phones to work in the United States. 

And because that manufacturer never intended for its phones to work here, they did not provide software or Hardware that is compatible with the AT&T voice network.   

It would be nice if AT&T just let phones self-certify, but during the shutdown process they could not do that. FCC requirements mean that all phones on the network must be capable of e-911 phone calls. Any phone that is not capable of voice calls is not e-911 compliant. 

While I don't agree with the way AT & T handle this, which is probably the worst transition in history, they do have the right to operate their Network the way they see fit. And since you are under no contract or obligation to stay, you can go to another Network.  T-Mobile's primary owner is a German Telecom and it does not operate as a 'US provider'.  Since it operates more as a European or worldwide provider it accepts phones that are made for other countries, very likely your phone will work just fine there. 

    If you wanted the freedom to move between providers you have to purchase a phone that is universally accepted.  

Explain all this to tourist that visit U.S. that have "International" phones. They would have to purchase throw away phones that overall effects your green house... 🤔 

Yes all government are given iPhone so no worries there.

The car meets the specs, even if not intended for U.S. market, but you can choose whatever gas 😲. 

@jmf0690 

Explain all this to tourist that visit U.S. that have "International" phones. They would have to purchase throw away phones that overall effects your green house... 🤔 

Yes all government are given iPhone so no worries there.

The car meets the specs, even if not intended for U.S. market, but you can choose whatever gas 😲. 

• It's your greenhouse too.
• AT&T really doesn't want prepaid customers for one month.
• All government doesn't get "iPhone".
• You can put whatever gas you want in your vehicle as long as it meets all the other requirements. It's not going to be worth it to bring for a tourist...

The bigger question is why Xiaomi is to chicken to enter the US market.  They may just be scared of apples 50 percent market share in the USA or Samsungs 24 percent of it.

@jmf0690 

Explain all this to tourist that visit U.S. that have "International" phones.

That's ok. U.S. citizens get mad too when they find out their phone doesn't work in all countries. There is not a phone that works everywhere. Research before you travel is important.

They would have to purchase throw away phones that overall effects your green house... 

Umm, that would be your "green house" too if you live on Earth. There are recycle/reuse programs to help.

Yes all government are given iPhone so no worries there.

That is absolutely false. There are government Android phones. And to an extent Blackberry phones as well. Though with the 3G shutdown, that may be the final end of life for Blackberry users. (hope I don't have to go through those all again for final turn-in).

Bottom line: You have a phone not bulit with intention for the U.S. market. Even if it might be physically compatible, it did not get certification as required by AT&T. For the phone to be used on AT&T's network, it must meet their requirements.

That means you either get a phone specifically certified to work on AT&T or you go with another provider. That is the choice you must make. Your attachment to your phone does not change AT&T's requirements.