MTN

I contacted MTN to cancel a contract I had with them as I am not working at the moment. 4 months later they are still billing me and now claim that I have 3 contracts. I have emailed , phoned them and even had an affidavit sent to them, no response, just billing me. My credit score has dropped by 29 points as it is now reflecting that I have not paid my account for 4 months. My emails and calls is falling on deaf ears. I am at wits end and don't know what to do next.