incorrect billing

I cancelled my upgrade and thereafter cancelled my contract in December 2015. My account was paid up and Vodacom is still owing me R310 for the reversal of the admin fee from the upgrade. Thereafter, the IT department made a provisioning error and did not switch my line to prepaid. I have been billed for a \month to month contract' for January even though the error was made by Vodacom. My bank account has been debited on 1/03 for over R3000 in error due to the repetitive mistakes made by Vodacom. They have charged me over R1900 for a handset which I returned in December 2015. I have the documents as proof and the details of every person in Vodacom whom I have been dealing with. I am now sitting in debt as a result of this huge mess up."