Unfair Default listing while disputing account

I had 2 Tracker accounts which I cancelled as I had sold the vehicles they were installed in. The one tracker unit was cancelled in December 2013 and Tracker stopped Billing me for this unit. I was then told that I owed an amount of about R480 for another unit which I had cancelled in 2014, I then paid this and only then Tracker cancelled the unit. after I had cancelled the second unit in 2014, I then started getting calls from debt collectors telling me I was owing tracker, I then laid a complaint with tracker and a few people called me to say they were working on complaint, after these calls I never heard from tracker and I later learned that they had listed me on ITC. During the time of my complaint, tracker did not list a default under my name, the account they listed had not been debited for over a year therefore I assumed that it had been cancelled as I had requested. I have spoken to attorney which are representing tracker and they have said they will not have my name removed and they were instructed by tracker to collect. As of a result, I have been declined credit due to this unfair listing.