Transfer of Responsibility

Hello, My friend and I were on a shared plan for years. we finally decided to split them up. i was staying with tmobile where as she went to a new carrier. She canceled her line and the Tmobile tech told her she would receive a bill for the equipment she owed in her name since she was transferring it and canceling the line. so now i just got my first bill without her and her equipment charges are still on my account even with her line canceled. i need to know if we can transfer the responsibility of the equipment payment to her since her line is no longer on my account and that is what the tech told her would happen. i didn't want to get stuck with her $1500 bill for 2 phones she broke. im not sure if tmobile made a mistake or not and how we can fix this so. all i know is i cant afford her equipment charges and i will have to leave tmobile if its not resolved.