MTN refuse's to cancel my contract 3 months in row

My first cancellation request was in September last year and MTN failed to cancel my contract. I have contacted them every month and the last was on the 26 January 2016 to please cancel my contract but they failed to , apparently they escalated to their retention's manager but still no one contacted me, when i called the call center , they unable to help me or put me through to the correct dept. This is terrible service and i wont advise anyone to stay with MTN or get into business with MTN.