Cell C overcharges with contract expiry without concent

I had a CELL C pinnacle contract for the past 2 years with promotional data. CELL C no longer offer these contracts, so I upgraded to a new contract with cell c. Firstly I asked for a media play 4GB TOP UP and it was upgraded to a normal contract. I was now changed R1350 for 10G of data which was part of the old contract which was suppose to be free. Without my consent the amount went off by debit order!