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JMoLuv70's profile

New Member


2 Messages

Friday, April 29th, 2022 9:18 PM

Is AT&T Flagging and Disabling SIM for Specific Phones in The US for use on their 5G Network

I always buy factory unlocked phones for use on GSM networks since I travel and plan to travel outside of the US. And I always select phones which are unique and unpopular. 

Anyways, I was informed, in the summer of 2021, that my phone would no longer work on the AT&T network because of compatibility issues when AT&Ts 5G rolls out in 2022. I usually keep my phones for 5 years just like my computers. AT&T offered to send me a phone that was not even comparable to the phone I purchases with advanced specifications, dual sim and the ability to add additional storage up to 256GB. 

I talked to the Customer Service rep and when discussed the phone I have currently with the phone that AT&T wanted to send me. It was noted that the replacement phone was not comparable. I kept the with the phone with the hopes that there maybe a firmware available by the time 5G rolls out. 

Phone was still working until April 17th with a result of SIM unregistered error. 

First issue I had was in March when traveling to JFK Airport on my way to France. Phone stopped working about a half hour away from the airport. Great. I then flew to France where my phone worked effortlessly in CDG airport. All over France, even in the metro. I have the international plan as an addon to ensure that I have service when traveling. 

Traveling back from France, the same issue. Though when I was about an hour away the phone connected back to the AT&T Network. This is good.

Then I travel from BDL to PHL (Philadelphia International), and the phone fails in Philly. I had to buy a phone because I was stranded the first day without access and that new phone, I got from Best Buy, because the AT&T rep in the store said they had none cheap to be used temporarily.  I paid $159 for the phone, Moto G Pure, which is supposed to be compatible with AT&T, but the Best Buy rep was unable to activate the SIM. 

I return back to AT&T. It takes a while. I get another SIM, eventually after some finagling it works. I get back to my hotel switch the SIMs phone. I works for like 3 minutes then fails. I put it back in the Moto G Pure. Doesn’t recover. I go to another AT&T store, I’m there for more than an hour and 2 SIMs later and the phone is still failing. I then check out T-Mobile’s international plans and explain my issue with the phone I want to keep. They perform a test where they put a T-Mobile SIM into the phone and place a call. And it works. It looks like T-Mobile might be an option.

It looks like BYOD might be an issue when connecting to the AT&T network. 

The list of phones that AT&T provided, that will work after the transition were existing phones and appear to be even model specific. 

It appears to me that there was a handshake and a verification between the phone and the SIM card. So I was unable to move the SIM between phones.

After going to AT&T multiple times (5) and T-mobile twice and being without a phone for 4 days, I called AT&T tech support. They were able to refresh the SIM with the phone to get it working again and this took about 15 minutes with a reboot. 

At one of the visits, I asked if my account or SIM could be flagged, and it was a definitive, no.

I am now searching for a new replacement phone not branded, to be used on GSM networks, and have the question:

Is AT&T flagging and unregistering SIM for phones, make and models not on their whitelist, using their 5G Network?

Accepted Solution

Official Solution

ACE - Sage


118.1K Messages

2 years ago

Some of your terminology is incorrect so I'm going to use correct terminology.

If you use a phone that is not on AT&T list of compatible, whitelisted, unlocked phones, your sim card is suspended until you replace the phone and contact at&t with an IMEI that is from an acceptable phone.  And then use that compatible phone, otherwise your sim card May once again be suspended.

This is the list of unlocked acceptable phones.

Non carrier branded phones that will work on AT&T

There are a couple of notations that the phones must be running current software. You also must have a SIM card that is capable of HD voice.


This is not a 5G issue. AT&T advertisements are honking their own horn about 5G which is still new and unreliable technology in some areas.

This is all about LTE and voice over LTE. AT&T is particular brand of voice over LTE is called HD voice and it is slightly different coding than is used by other service providers. Because AT&T is required to have phones that are capable of voice calls in order to meet the FCC requirements for emergency 911, all phones on the network had to be certified that they did work with HD voice, or AT&T would block them from the network.


New Member


2 Messages

2 years ago

Thank you very much.

I’m sure my terminology was and is all over the place as I’m trying to figure out the exact capabilities that a new phone requires to be accepted on the AT&T network. 

It appears that because AT&T is using slightly different coding than is used by other service providers for HD voice and e911, it appears that any phone not certified by AT&T for use on their network will be automatically blocked per the FCC requirements. 

So I have 2 options: 

1. Purchase a phone from the whitelist, not model specific.

2. Switch providers. 

Thanks again for your response. Have a great day.

ACE - Sage


118.1K Messages

2 years ago

Yup.  Correctly diagnosed. 

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