MTN owes me money for data used by them.

After two months of using my new MTN ****le, which I had on a 24 month contract, it had a technical fault. After sent away for repairs by the MTN department, it came back fixed, however, with an additional data account of over a R1000.00. Upon enquiry MTN confessed it was used by an employee in the technical department (Milnerton), but passed the buck from one department to the other. Apparently the 'sim' card was supposed to be removed before sending the ****le away. The amount was then deducted via a debit order from my bank account. When I asked what I can do to get my money back for data that I paid for but never used, they said that I should go to the police and make a complaint of *****. The employee who had used the data, has since left the company. I have been to the Durbanville branch in Wellington Str. a couple of times, but nobody wants to assist me, and I get told the manager who must help me is busy, all the time.