All incoming and out going call stop working after 3G sunset

@michael_barnard71 
Do you have a similar solution for an A71 5g?  I have the exact same issue, and ATT has been no help.  It was working up until March 1.

@alderon57

The 6t is whitelisted, unlocked phone.  It should have worked without fussing . 

The only A71 that is whitelisted is AT&T own branded device. There is no unlocked A71 on AT&T whitelist. 

@formerlyknownas 
My device is an SM-A716U1; which is whitelisted on three ATT documents.  Yet it still doesn't work.  If someone knows otherwise, I'd like to know.

Based on other posts here the U1 isn’t on the list. I’ve never looked at the list so not sure 

@Constructive 
ATT document - "Service Capabilities for your unlocked device", 3/9/22, Page 4 - Samsung / Galaxy A71 5g (A716U1) - "Capabilities = HD Voice / 5G"
ATT document - "AT&T smartphones that support Wi-Fi calling as of 11/10/21", Page 2 - Samsung / Galaxy A71 5G
ATT document - "These phones will still work on our network after we phase out 3G in Feb 2022", Page 1 (1st item) - Samsung / Galaxy A71 5G (A716U, A716U1)

Either AT&T is lying or woefully misinformed about their own system.

Your right it's on the March 9 updated list.   

How old is your sim card? And is the phone running up-to-date software?

The SM-A716U1 is on the unlocked list.  It should work, but it doesn't do Wi-Fi calling.

@formerlyknownas 
The SIM card is brand new, and the latest software is due any day now from what I've read elsewhere.
I want to solve this now just on principle.  I used this phone most of last year, and up to March 1st.  They aren't making me buy a new one.

If it requires a software update, hopefully it will not be long to get it. Unfortunately you go by the provider (if carrier specific) or phone maker (if manufacturer unlocked) on their software release schedule. Not something you can make happen sooner, regardless of principal.

@JefferMC  the A71 supports wifi calling that won't be an issue.Leave the sim card in it and turned on for a couple of hours.That will give the server time to update and send the OTA to enable the support it needs.