Harassment from Cartrack

What a harassment from Cartrack. I called in in May to cancell the device contract with them as I was trading in the car. They always phone me and tell me to pay still. My question is Who are they tracking now? I no longer have the car in my possession.Can't they even track the vehicle to see that it's now out of usual route? I am concerned about the safety of the drivers/cars tracked by them.