Poor service from MTN

I had a contract with MYN that expired more than a year ago, 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, no reply. The cell no is not active any more since 2022.. So I wrote the debit orders back, now my scoring on Clear score is affected because it show an unpaid amount every month. How on earth can one make contact with MTN?