Incorrect Billing charges and bad service to resolve

I really dont have a problem with paying my account and cancelling my line. I have cancelled my telkom line 3 times at cresta and today i receive an account where i am being charged penalty charges and this is truly poor internal process and unprofessional conduct. In December I have a telkom line 011 431 445 and i had a credit balance of +/- R600. I went to transfer my line as i moved house the lady instead of transfering the line cancelled the line and gave me a new number the queue at the time was horrible and i stood more than 2 hours in line so i accepted. The credit balance was not transfered and 3 times i attempted to resolve standing for hours in the cresta telkom offices to settle and cancel. nobody could assist and advise on the credit balance now i am being charged penalties and penalties and am sitting with a balance of R1500?????? This is unfair and i cannot be expected to pay this amount for a line i have not used and a line I asked to be cancelled when I was in credit.............