MTN charges despite no active contract

Cannot believe this level of service. I canceled my contract 3 months ago and have been billed every month. I have 2 current contracts with MTN and now I have had them canceled because I stopped payment as a result of them overcharging me for the past 3 months. They have deducted +1300 rand from my account and provided no service. I have phoned and emailed more than 10 times and I’m at the point where I do not know what to do.