MTN DOES NOT WANT TO CANCEL MY CONTRACT

MTN has been giving me a hassle over a month to cancel my contract i have called the call centre with no help they keep telling me that they will also send an email to retentions and i have also emailed to retentions numerous times to cancel my contract. i have been receiving automatic replies but till to date my contract hasent been cancelled.i have also sent an email to complaints@MTN and said ill get a feedback after 5 days. i have been a loyal customer to MTN but now i do not need my contract anymore but now its a problem when i have to cancel my contract. i want to be migrated to prepaid but all they do is credit my account with airtime and data at the end of the month theyll send me an invoice to pay. i do not need a contract any more it is very unnecessary to have it especially with MTN's high rates. MTN cancel my contract that is all i want from you guys,i really do not understand why is it so hardto cancel my contract