Phone won't make or receive calls

Our apologies for the delayed response, @SaneTezz. 

It appears your unlocked Samsung Galaxy A51 is no longer compatible with the AT&T network. 

We encourage you to visit our device web portal and follow the steps to redeem your free device: 

• Validate primary account phone number and 6 digit SMS code
• Validate billing zip code.
• Validate shipping address.
• Accept or decline replacement device.
• Review/accept order.

Let us know if you require additional assistance, and we'll step right in to help!

Sydne, AT&T Community Specialist

Hello Community,

We have been reading through this thread, and appreciate the feedback and comments included.  We also want to thank all the posters who have been jumping in and trying to help answer questions and provide support.

There is a lot of great information included in this thread, but we wanted to make sure one troubleshooting step was called out, so it isn’t missed.

• A common issue is that some or all LTE service may be toggled to ‘off’ within the device settings inadvertently.  This can cause both voice and data issues depending on the device.

 To Resolve:

• First:  Determine if the device is “HD Voice-capable” (a.k.a. “LTE Calling”, “VoLTE”, or “Voice over LTE”)
  • If no, you will need an HD Voice-capable device
  • If yes, but not AT&T branded, you may need to update the device software.
• Second:  For those experiencing loss of Voice and/or Data service, check the following settings and then power cycle the device. 
  • Apple - based on iOS version:
    
    • Settings->Cellular->Cellular Data Options->Voice & Data->LTE (select LTE option)
    • Settings->Cellular->Cellular Data Options->Enable LTE (select LTE option)
    • Settings->Cellular->Cellular Data Options->Enable LTE->Voice & Data (select Voice & Data option)

• • Android
    • Go to Settings > Connection > Mobile networks > Enhanced LTE services and select on.

Once complete, please ensure you power your phone off and back on to establish a fresh connection with the network.

Thanks everyone, and please let us know if we can assist further.

Tim, AT&T Community Specialist

Hey all, read this thread. Basically skip to the end to get all the info on flashing the correct Android 12 firmware for THE GALAXY S10. 

If you have another phone... Same idea. Find the correct firmware and download Odin... Flash it yourself. 

The issue with unlocked U1 galaxy phones is the stock firmware does not have ATT CSC files. they are custom for VOLTE. 

U1 phones have no carrier files. So you basically have to flash the U version of the firmware.

https://forums.att.com/conversations/samsung/phone-cannot-make-or-receive-calls/6216dd5c87306e2032e14d9e?commentId=622e36073c3dbc77d9635266

What is the model of your Samsung phone and your miles Apple device? 

AT&T shut down 3g service and that could be the cause. 

Here's the whitelist of phones that should still work. 

Whitelist

I have same issue with my Galaxy Note 10+ 5G. Suddenly started last night or this morning. If its not phone issue or AT&T, its gotta be Russian hackers ;-), but still need it fixed.

Yeah sadly that's not the issue.   I have a Samsung galaxy a51 5g so it's still good. 

I would go to the closest store and get a new SIM card and see if that fixes your issue. Other than having a att network reset done on the phone, can't think of anything else that would be causing it since billing is good. 

@blkopns 

What's the exact model number for your phone? Is it unlocked or AT&T branded?

It's sm-a516u and it's unlocked originally sprint. 

@SaneTezz 

Did you buy it unlocked and put it on sprint? Based on the list, yours should work if that's the full model # from the phone.  So yea I would try a store and a new sim card and see if that works