MTN overcharging

Writing on behalf of my father.

My father took an early upgrade at MTN Cape Gate. He was advised that there would be a penalty however when the first month came they had deducted more than the salesperson stipulated. He went to MTN Cape Gate and was advised that they need to sort it out at accounts in order to process a refund. The next month the same thing happened again and this time a different amount was deducted. He had to go to MTN again and they said they are sorting it out. A month later the same thing happened and my father was advised that his old contract is still active and that they are deducting both. Now after my father reversed the deduction his phone has been cut off. He went to MTN Cape Gate again and was told it would take two days. It went on yesterday but this morning it was off again. This is unacceptable as my father is a policeman and needs his phone on the road. Please rectify this situation asap