Telkom has messed up my credit profile, and charged me for months of service when I was disconnected. I cannot pay this

I'm probably wasting my time here and will probably need to escalate this to the relevant financial authority before I can make some headway on this but telkom does not contact me yet I get an adverse listing on my credit profile!! Furthermore my services were disconnected but still got charged for additional months and interest on top of that!!! I was a loyal telkom customer but ported to another network frustrated because of the constant issues!!! How can I owe 5k and be listed as a bad payer when you never contact me? How can u charge me for months I did not use the service? This will surely be taken up further