I can see the anger here. AT&T is not very smart, and at the same time quite slimey. They should have known this change was going to peeve the tech crowd (Not smart for PR). Then this happens, kinda like pooring gas on the fire.
"A PR person working for AT&T (but not an AT&T employee)" wow, how slimey. So they're using non-employees (contactor I assume) to contact angry customers and then make their threats. Did they completly forget what PR stands for? I worked for a large tech firm once, they hired contractors to do the internal IT, saves loads of cash you see as these contracters were willfully underpaied; maybe this is the reason? Or is this so they can later say "well yeah but it wasn't really us". So angry about a silly email. please. I guess they don't know of email blacklists... AT&T, I'll give you a hint here, your making lots of money, shut up already!