TELKOM NGN ACCOUNT IS *****!

I have had a Telkom NGN account listed on credit profile. This after I cancelled my contract in Dec 2017 and had to pay off the account. I have tried to get both Experian and Compuscan to rectify this error. I sent them a paid up letter of what I owed but cannot seem to get the NGN account removed. This is bull**** as it sits on my credit profile as an account in arrears. Nxa!