blacklisted

my ex open a gym account on my behalf and he didnt tell me now he didnt pay the gym the gym blacklisted me not him and i didnt sign anything from the gym i didnt even go to the gym i went to the gym an ask them why they blacklisted me because i dont know anything about the gym ,i didnt even come to the gym can they remove me from blacklist, they told me i must ask my ex to pay how can i tell someone i dont even see to pay i want the gym to cantact him and blacklist him not me i didnt join the gym , the gym give me the copy that he signed i dont know want to do with those papers i just want them to contact him call him remove my name from blacklist .