Unauthorised debit orders for cancelled Cell C contract

Good day

Debit orders for my cancelled contract kept going off after I personally went into a Cell C branch where they connected me on the phone to the service centre. They assured me it was cancelled. I called Cell C customer care on numerous occasions thereafter because the debit orders continued to go off for random amounts up to R1300 (the contract amount was only R200 with a limit block). I had no alternative but to close my bank account as the bank informed me there was nothing else they could do about unauthorised debit orders. I reported Incident: **********31 in 2018 and was assured that it was resolved only to find out now that there still reflects an outstanding amount on my credit report. It is impossible to get assistance on the phone or in person from a Cell C branch. How do I get this rectified?