I guess this is more of an informative post. I have First Net, which is a 1st responders, military, ect phone network that is built by AT&T. Last week they shut off 3G, and because of this, my Note 20 Ultra, unbranded and unlocked, won't make any phone calls nor receive any, but yet I can get texts and use my data. So if anyone having similar issues, it's AT&T, not you or your phone. I only found out last night and verified it this morning. After working with customer service, they put in a "ticket" and will contact me. So I hope nobody is having the same problem, but yet I do so I know if it got corrected.
Anyway, have a great day!
Anyway, have a great day!