They just keep calling and calling. I tried calling back but just get a voice mail that it is attempt to collect a debt. I am not behind on any bills.

they just keep calling and calling saying I owe at&t money.... which I dont

This is a collection agency for AT&T.  They will pester you until you pay them.  I don't even have AT&T and I'm tempted to pay them just to get them off my back -- but then the man (with a heavy accent) told me I would need to "call the AT&T to let them know you paid."  What will happen if I don't?  Will another collection agency start bothering me?  Not sure whether this is just an error or what the problem is, but even though I don't have AT&T, this man knew ALL of my personal information -- asked me to verify my SSN, my address, my DOB, and so on... which he had.  Scary.