I am in the middle of a "Last chance for you, AT&T" situation. I went to Best Buy because I was having an issue with my phone, and while I was there I was going to look into switching to another carrier. They had an AT&T tech person there, who started a grief ticket about the issue I was having (the man spent about an hour on the phone HIMSELF with AT&T on my behalf). They called me back, the tech on the phone listened to my gripe, saw for himself the error msg, and forwarded the problem to an engineer. I was told I should hear back in a few days.
If I hear back in the allotted time, and if they resolve the issue, will be the deciding factor. I DID learn one thing, though, that may be of interest to the rest of the people having the same problem: they have a team trying to figure out what the problem is, they ARE aware but haven't discovered the root cause yet, and until they find it, they can only work it on a case-by-case basis. I'm guessing maybe the root cause appears different in each online account(?)
I think it would be EXTREMELY helpful if ALL of AT&T tech support was aware that this is a problem and they could let the customer know at least THAT much when they are contacted.