Horrible/unacceptable customer service

I have receive an unacceptable customer care/ behavior from MTN sales personnel. I had a contract with them which was cancelled by one of the staff member after my upgrade that was processed on the 24 October 2023. On the 25 November & December 2023 MTN debited R1118-00 which we never agreed on when i signed the contract. when i made the follow up they told me that it was changed to month to month. I have made several calls to fix this matter but they didn't assist me.