Telkom continues to bill me unauthorised

I had a 24 months cellphone contract with Telkom which had to terminate end of September 2017. According to Telkom I had to fill a cancellation of contract form for them to terminate my contract, which I did and they had acknowledged receipt of the form. But typical of Telkom, they won't let me off. They continue to Bill me . I even went to my Bank to stop the debit. If it refuses they change the billing codes to access my money and they continue to deduct my money unauthorized. My name is Marumo Frank Mothemela . My contract cellphone no. to them is ********** 030. My active contact cellphone no is ********** 056. Please help out of their arrogance.