CANCELLING OF DATA CONTRACT

My husband took out a mobile data contract (no ***) in August 2018 but sadly passed away in October the same year. I went to your branch in Cape Gate Cape Town, and they suggested we only change the bank details and then I can carry on with the contract. In August 2020 the contract expired, and this is when my problems started. In September I went to Cell C in Kathu where I gave them the death certificate, both our id's and the letter of executorship and told them to cancel the contract. Every month they deduct the premium but then I reverse it. I have made numerous calls to the call centre and to the retention department and sending emails with the necessary documents, but without any success. I also went to Cell C in East Rand Mall Boksburg where they also sent the documents (retention department) and told me I should receive feedback within 72 hours. The last time I phoned was on the 25th of November 2020, when they send me a reference number *** and again somebody will contact me within 72 hours. Nothing happened, no premium was deducted in December so I thought finally the contract has been cancelled. But yesterday, 6 January 2021 they deducted R1600.00 from my account, which I reversed again this morning. I don't know what more I must do to get this contract cancelled. I have not used any data since August 2020 and I have destroyed the card. I cannot stop the debit order at the bank, because they told me Cell C will just use a different reference number. Can somebody please help me!