Very upset customer

I had a cell c contract and the contract expired. Was told by cell c I had to cancel a month before the time which I did. I also phoned them 4 times to confirm that contract was cancelled and only the last instalment had to go off which firstly did not go off because they kept on debiting on the wrong dates and not the date we agreed to. Eventually the debit did go off. I then phoned again and was told they can not retrieve any information as the number is now a prepaid number. Cell c cost me R800 just in bank charges because their admin is ***********. Then to make matters worst they kerp calling to say I owe them a installment but yet they can not retrieve any information. I want the bank charges paid bback yo me becaude it is their incompetency that caused this whole mess in the first place.