Dont deal with MTN

We took out a data contract but there is only very intermittent data signal in our area and have therefore attempted to cancel the contract. Believe it or not but the store in Cradlestone told us that they cannot do it and they acknowledged that attempting to contact the call centre is impossible. We have written to them formally cancelling the contract and received a reference number but when we phone to confirm the status are told that the reference number doesnt exist. It then gets worse. We are on an old system and they cant access the information. How then do they manage to bill a client that doesnt exist? So far another 30 minutes of my time spent trying to get hold of someone to assist. Our bank has advised that this is a common occurrence with MTN. How do they continue to do business?