My mother received the same call. She did recently move, but her mail is forwarded to me and her bills are only sent electronically. Not legit.

We received a voice mail from this number so we called it back. Spoke to a man who identified himself as William - he said he was not allowed to give out his last name when we asked. When we asked what this is in regards to he said "this is about mail being returned to us" - he said that without even asking our name. We did not give out our phone number and asked to speak to his supervisor. She gave us her first and last name, which sounded fake and prepared. They were both rude. We asked her where they are located and she said North Carolina. We asked to please speak to someone else in the office she refused, she said "why would you want to speak to someone else?". I don't know what scam they have going -- but this is definitely not AT&T. They didn't even say that the call was being recorded for quality assurance - which is standard no matter where you call these days.

Shows up as unknown caller.  Legitimate ATT calls probably leave automated messages and show up on caller ID as AT&T