Refund on my account

I ve been with tracker for over 10 years for all the cars that I ever owned. I called in September to cancel and open a new account since I bought and sold an old car. They debited my account in October and November and after countless communications they revert back to me and to my surprise they said they will only refund half the amount that I paid because the car had 2 units. How is it possible that you only cancel one unit and leave the other unit on the car that I dont have anymore. Can tracker stop disrespecting me please and pay back my money