Paid up letter request

Extremely disappointed with Telkom. I cancelled an account with them 3 years ago and was still being billed. I had no choice to pay a settlement value which was done 3 weeks ago but no paid up letter has been supp**** since. Many attempts of receiving one has been made with no success which is currently affecting my credit negatively as Telkom has listed me on ITC as a bad payer. After 3 years they list me, I pay them a large amount immediately but I am now begging them for assistance on their mistakes. Someone please assist me in getting this resolved. Thanks