AT&T Radiant Max 5g connectivity issues
A couple of months ago I bought online a new AT&T Radiant Max 5g for my prepaid account. It worked just fine using the 4g LTE network up until a couple days ago, then it started dropping mobile service, and I'd only get the "Emergency Calls Only" message. I had the sim card replaced, only to have the same issues. It would drop mobile network for a while, then randomly come back up, only to drop again after a few minutes of service. I have a cheap backup phone that I put the sim card in and it has no service issues, so neither the sim card nor the prepaid account seems to be the issue. I have power cycled, data reset, reseated the sim card, even did a full factory reset, all to no avail. Location isn't an issue, it's had this problem at several places around town, but my backup phone on the same network hasn't. I'm starting to think there may be a problem with the phone itself, unfortunately since I bought it third party I don't think the warranty will cover it. I'd really hate to get rid of this phone, it worked great until recently, but I don't know what else to do. Any ideas?