MTN Retention Department is Non Existing. It Sacks!!!

I have been trying to cancel my sim only contract with MTN since October. I sent emails to *** and nothing is happening. Why is it so easy to get a contract but when you want to cancel no one respond to email. I even post on Twitter and was told that we are looking into it. It has been 4 weeks and nothing has been done. All I want is to cancel my contract and make it prepaid.