Bad bad service

I recently bought a car and the tracker was installed before the car left the garage, I paid upfront for the 3 year contract however now my tracker is not working because they say I owe them and I have been handed over to the 3rd part, I have been trying to solve this issue for over 6 months now and nothing is being fixed instead they transfer me from one agent to another with no assistance at all. My worry is that what if I get highjacked or something nd the insurance realise my tracker it ain't working then I have lost my car because if their incompetence am not hsppy at all and am willing to cancel my contract with them pls help