Unauthorized debit by MTN. Poor Service. No answer when calling in

I have been debited R579 which was not authrorised by myself. The standard debit order is for R299. I have reversed this debit order which was at a cost of R40.

I have called in to the retention department and waited on the line for 12 mins. with no answer, on the 26/08/2022 from ***, call was terminated at 9h14.

Now they want to charge me an exorbitant amount to cancel my contract because i was unhappy with the poor service.