Unhappy with Telkom Cancellation

We cancelled our ADSL usage in December 2020 and are still being billed. I called in to find out what is going on and according to Telkom we never cancelled the ADSL. Yet when I called and spoke to their Technical Department, they said we have not used ADSL since Jan 2021 yet we are being billed each month. I had to re-cancell our request and have decided to cancel both the ADSL and Line rental now as I am extremely upset with their service. I have maintained an excellent credit record and am now in fear of my name being blacklisted. They now claim we have to give 90 days notice from the date of which I re-cancelled in July which means the amount due will be even worse and my name will definately be blacklisted. I requested that they credit the ADSL fees but they said I can only dispute this after 90 days and once the line etc has been completely cancelled. As it stands our line has been suspended. Please help as I really dont want to be blacklisted for an error on their side. Thank You. Belinda Naude (Telkom ADSL Line in question ***)