You have choices with AT&T DSL. Learn how to install your DSL with a non-AT&T modem.
Non-AT&T modem installation
Setup and registration for non-AT&T modems
If you are using a DSL modem that was not provided by AT&T, there are special instructions for you to setup your equipment and register your account. Please follow the instructions in the AT&T DSL Self-Installation Guide for Modem Equipment (PDF 2.8MB).