Someone used our address and their name to open AT&T cell phone account
Several months ago someone opened an AT&T cell phone account in their name using our address. We are the original owners of this home and we do not know this person. We have never had any renters here. We have been getting their cell phone bill each month. When it first happened I opened the cell phone bill by mistake and called AT&T customer service to report the problem. They said to mark the mail with "return to sender" and that they could not do anything else about the problem. We have been diligently marking every piece of mail with "return to sender" however, we are still receiving this bill every month. What can we do about this problem?