MTN cancellation is BAD or non existing

We are having issues with MTN, they keep on asking for money after we already have cancelled the contract, received a cancellation refrence, and paid the amounts that we were told to be pay before they can cancell the contract. After so many phone calls, visists to the local mtn shop, the issue is still not resolved. When ever you phone the cancellation department, holding on for 45 minutes and longer, when they need to give answers on your query, you get cut of "conveniatly. TOTALLY UNEXCEPTIONAL, and therfore you just get billed again, and they keep on making money