How can cellular phone company charge you for phone you did not sign contract on?

in March 2000 or 2001 that I did buy phone else has done that shut down the first suppostly, and then was reported stolen to the phone to shut down, thought that was the conclusion of that, but later they turned off my new phone to the old phone he was using oakhloma with oakhloma number.so the paid my bill, but nothing else than to turn the mines off.and he reported to the entire cooperative credit and the 3, still on my reports accreditation .