Cancellation

Bad experience... I forgot to change my credit card as the card expired and was in areas for abt 2 to 3 months. I have notified the team and thought i might as well cancel my contract as i have not used the gym for almost 2years..upon paying the outstanding and closing the account i was handed over to credit works.. These guys are calling me for the past 2 month saying that i owe them. I have forwarded the proof of payment with a letter confirming the account is paid up to date and that it is cancelled. Till to date i am receiving calls saying i am handed over and i need to pay up. I have heard about ppl ending there contracts and still be debited and handed over. Is there someone that will help sort this out!