MTN south Africa ****

I had a contract with MtN that I have paid off in January 2023 this year , but MTN kept on deducting the premium although I tried to cancel the contact several times. There is no way I can get hold of them. I went to the MTN shop, they say they don't do cancellations in the shop any more, I must send a mail, which I did, I don't want to reverse my debit order as this would reflect bad on my credit score.. How on earth can one make contact with MTN? Everytime I call they do say that it does reflect on the system that is was cancelled but as to why they don't clear it on their side I don't know. They just **** us an keep deducting my money