CONTRACT CANCELLATIONS

I am so disappointed with MTN, it is pathetic. I am trying to cancel my contract. Let me tell you that they put you through and then you are stuck for the rest of the day or until you decided to put the phone down. They just do not answer the calls. So what am I suppose to do to get my contract CANCELLED. The stores do not help all they say is phone 135. ANY HELP WILL BE APPRECIATED!!!!!