What do i do about a debt from et acceptance that is not mine?

I HAVE A $1200 DEBT FROM ET ACCEPTANCE LLC THAT IS NOT MINE. IT IS FOR A PHONE BILL FOR A PHONE THAT I NEVER HAD. IT IS FOR SOMEONE WHO HAS MY SAME NAME BUT I NEVER LIVED AT THE ADDRESS THEY HAVE NOR HAVE I EVER HAD THE NUMBER THEY HAD OR EVEN RESIDED IN THE SAME COUNTY THAT THE ADDRESS OR PHONE NUMBER IS IN. I CALLED THEM ABOUT IT AND TOLD THEM THIS AND THEY SAID THERE IS NOTHING THEY CAN DO. WHAT DO I DO? HELP! PLEASE!