Bad service re-cancalletion.

Very unpleasant service from Matrix. I have sent written cancellation for my tracker since I traded in my car. This written cancellation reached them a month ago and now I am being told that I need to pay double for cancellation and for July meanwhile my old car had already been traded in June which I had already alerted them in writing. Their consultant one Phindile Majola as she introduced herself was overly rude and sarcastic, so much for being their customer for over 8 years and of consistent payment. They do not even seem concerned to retain their customers, since they did not even ask whether I would be requiring a new system for the new vehicle.