Getting Blacklisted for a service never used

A year ago I app**** for an ADSL line, Telkom send me a bill without installing the device at my house, I went to the Telkom store in Rustenburg and they were not able to assist me, I had to talk to the billing and accounts department. After spending an hour with them over the phone, I cancelled the application and they confirmed that my account is clear. Only to discover a year later that its not true. I app**** for a credit check and saw that Telkom blacklisted me for R243.00 for a service I never used. 3 week ago I spoke to a lady at Telkom who listed my complain and said Telkom will send me a letter to clear my name because she can see I never used Telkom service. Today I tried to phone and Telkom service is bad, they are sending me from one number to another and now one can help me. I also raised a complain through the email address provided on the web page but still no answer. What can I do to get this fixed?