Wrongful credit listing on ITC

We were paying a monthly account for R199 with Telkom for use of their landline to enable us to have internet connection. We moved out of our house in July 2017 and gave notice to cancel this service 30 days prior to us moving. Afterwards my husband still received accounts requesting payment. Every time he would phone and explain the situation AGAIN and confirm that this was cancelled. 3 Months later he receives a call from debt collector attorneys requesting him to pay for a an account which was duly cancelled. Even visited Telkom's offices. After so much effort and phone calls they eventually wrote off the "debt" which wasn't debt to begin with and confirmed it with an e-mail. We thought all is well. Just to apply for a home loan now and to get a full and final rejection based on an incorrect credit rating. Yes Telkom had my husband listed at the credit bureau for a wrongful default and listed as "bad debt" written off during April 2018. This was not even debt to begin with as we gave proper notice and it is not our fault that their admin is so up to ****! You would think they would at least make the effort to remove such incorrect information from Transunion. We always pay all our accounts on time and we don't even have major credit card debt. So thank you Telkom for denying us a home loan!