MTN POOR SERVICE

Poor Service. I have had an account with MTN for 6 months. In those 6 months I have probably had about 2 months worth of internet connection. I have requested them to terminate my contract and to send me the termination T's & C's. I have had minimal response from them and have subsequently stopped and disputed payment on the account. Still no contact from them. I am prepared to return the router and sim or to pay the termination fee. but they just ignore a person. This could reflect on my credit rating. Who can I contact to finalise this issue? Please help! Somebody!