Unhappy ex-telkom user

I stopped my line with Telkom beginning January 2018. I have tried to stop it via the email channel, gave the application in by hand. I even took the cancellation application to East London to ask a consultant to send paperwork to their HO. No success. I was eventually told by a person in accounts department (after so many months of struggle) that they can't cancel my line as it was still with my ISP and I need to get them to cancel the line 1st. My ISP was cancelled in January already and they confirmed via mail that they do not have the line as my account was closed with them. Sent a cancellation mail again after phoning in to their head office in Feb with no success. I eventually got hold of a direct email address, Ashley Goordin at telkom who was able to cancel my account with struggle. I have asked Telkom to backpay for the last 3months , but till date I have not received any feedback from anyone at Telkom. Not sure what route I can take as because if I was behind 1 month my name would be black listed immediately. So I was forced to pay to keep my name clean.