Atrocious service from MTN

Once again we have issues with MTN. This is the third time our data sim has been blocked, regardless of the account being paid. The data is however slowly depleting which I cannot understand...The call center says they are unable to assist and we should go into an MTN shop, we go into the shop and get told to call the call center. I asked if I could cancel the contract and the assistant mentioned that only the call center will be able to tell me, which is exactly what the call center said about the shop. MTN’s general level of service is atrocious and I would honestly prefer to have this contract cancelled completely than continue to do the back and forth with MTN.