Unauthorised debit order

I had a WiFi contract with telkom, I called them early January 2026 to cancel my contract but to this day 25 March 2026 they are still debitimg my account. I have to keep on reversing the money which is costing me bank charges not to mention the inconvenience caused. The reason for my ending the contract was that when I was late with my payment they charged me R200 which I felt it was rediculous. Now they are busy sending me sms's that I owe them and they will blacklist me.