Do i have to pay a phone bill to a person who cancelled my phone service?

Someone added me to their AT&T phone bill, 3 months later, they decided to suspend my phone making it inactive. they are now telling me i have to pay them the monthly bill and either the cancellation fee or switch the responsibility of the bill to my name, which would cause me to pay $50 more a month. If do neither, they will take me to small claims court for not paying. So my question is, would i have to pay them, or would they win the case forcing me to pay? the account is in their name and i never refused to pay the bill, they kicked me off for personal reasons.