Tracking device safe and sound early warning.

Im an Altech Netstar client, i sold my car with the tracking device, now i want to install new device on my new car Altech is telling me i owe them R900.00 if i want to calcel previous account which was never mentioned to me that on cancellation of account theres fee to be paid. I decided to have the previous unit removed from the car i sold them reinstalled on my new car they say it will cost R650.00 of which they are the one which suggested that i remove the unit and reinstall. Now i wonder had i sold my car and didnot buy a new car this would mean il b paying for a unit which i dont even have. Now im stuck i dont know what to do. Altech is just demanding more and more money from me.