Fibre Cancellation Fail

I have been trying to cancel my Telkom Fibre since September 2020 (the process is too long to describe here). I finally managed to get it cancelled at a Telkom store and was provided with a reference number, mid-November. SInce then, I have had two debit orders deducted from my account, even after going to my bank and getting them to attempt to stop the debit order - to no avail. The debit order has still gone off my account. How can Telkom override a bank? I have an official bank letter saying that the debit order was cancelled, yet Telkom continues to deduct from my account... If I may offer any advice, rather use a different service provider - I was actually warned by the bank that I am not the first client with this problem.