Mobile billing forgivness

Last year I got xfinity internet and they had a promotion to get a free mobile line for a year. I didn't need it but my roommate was broke so I offered it to him and forgot about it. 

Fast forward to the present, turns out that roommate was crazy and semi-evil and I have no contact with him since moving out. Like I can't get ahold of him. He of course never cancelled the phone line and I forgot about it. I don't know if he had been using it or not. I however am getting the bill and it is overdue. Its about $120 and I don't really want to pay it because I had covered this roommate's rent and utilities often and I don't want to sink anymore money into this terrible relationship (he is still haunting me even after moving). 

So my question is: Is there any point trying to get this resolved with the company or do I just have to suck it up and pay the $120. I don't think there is anyway to get in contact with this roommate he was headed back to Mongolia and in a destructive cycle unfortunately (I'm not sure if he is alive TBH) 

Thank you