Incorrect amount debited

I recently took out a Sky package - in the middle of October. The cost for this is R2064 per month. Now for December my account has been debited by a whopping R5053 and when I phoned to query this the first consultant explained that one of my other lines was an \open line"and had accumulated a bill of over R8000 in 1 month?? I explained to her that the line she was referring to was infact on a Top Up package and so there was no way this would have been possible. She obviously was not able to give me a reasonable explanation and decided to cut off the call. I called again and another lady at the end of the line clearly had no explanation for the bill and just went on to say that what I owe and need to pay up. Eventually my husband called a third time and the consultant indicated that they had incorrectly billed us as the line in question was indeed on a Top Up package. The issue has been \""escalated\"" - reference number ***6. What I need is for this issue to be resolved immediately. Why should MTN be holding on to my money when it was clearly their error in billing me?? This is a huge inconvenience on my part. """