This is a customer forum, not ATT. And this is the cell phone forum, not land line service.
You can print a PDF copy of your phone bill up to 14 months in arrears. Access your online account and your bill history.
The information is only numbers and times, just like your current months bills.
If you want AT&T to send you paper copies, your will have to call them, and they will charge you for each reprint. It used to be $3 per bill.