MTN refuses to cancel my contract or attend my query

MTN is really annoying. I had a 36 months contract with them and on the 36th month, I sent a cancellation request. To my surprise 6 months later the bill was sent to my email. The account was handed over to lawyers and I settled it. To date, I am still charged on the contract. I am really disgusted because the store won't help. Emails are unattended, Facebook is also responsive but at their own pace but resolves nothing. If there was a minus rating, that's what they would get.