Impossible to cancel a contract with Telkom

I have been trying to cancel my mobile contract with Telkom since January 2021 with no success. My contract was due to end in February 2021, I went into the Cresta branch and requested the cancellation. The agent helped me to log in my request on line and I immediately received an sms confirming receipt of my request. However, Telkom continued to debit my bank account on a monthly basis for Data. When I enquired in April 2021, they told me that the cancellation job was closed without been completed. I then requested that they complete my cancellation which they promised to do. To my surprise, they continued to debit my account after my query. I then decided to block the debit order. Since the debit order has been blocked, they are sending me daily sms requesting payment of the outstanding amount, or risk to be listed with the credit bureau and send my account to the attorneys. This is totally unacceptable and I want a refund for the amounts debited from March to June 2021 and the cancellation of my contract