I'm experiencing the same thing. I purchased an unlocked S22 Ultra to upgrade my unlocked Note9. I'm on FirstNet, and have been since 2019 using my Note9. After a week of back/forth with customer support, and being escalated twice, FN has now come back telling me that my S22 Ultra isn't compatible and that I need to upgrade. I'm sorry - upgrade to what? The S22 Ultra is the top-of-the-line flagship from Samsung. It's listed on their compatible device list, only as an AT&T branded device, not an unlocked device. In fact, if I go to their compatibility page (
https://www.firstnet.com/checkyourdevice.html) it tells me "Great News! This device is compatible with FirstNet." The issue is that unlocked devices aren't whitelisted, so therefore they do not work on FirstNet network.
I'm going to try a solution from reddit user Romeo_Golf:
- Go to an ATT store and beg them to give you a new orange, regular ATT card. Just say you need the card, and that they don't need to activate it. They'll probably give you crap like me and say bla bla this, bla bla that. Eventually they said the card won't work because they didn't activate it, but you just need to get your hands on the card.
- Go to your firstnet.com account, login, and click Manage Services and Billing
- Under the drop down menu of "I want to:" click "Change device IEMI/SIM", along with your wireless number.
- Click change next to SIM/ICCID and type in the new sim ICCID number from the card in step 1.
- This is where it gets a little funky. I had to remove the " First Priority SubPaid Prim Level 4 Priority" and substitute it with "Dynamic Traffic Management Public Safety FNSP".
- Continue through the prompts and after verification it took about 20 seconds for the old card to die out and the new one to activate.