Useless cartrack service

I have had to endure bad service from CarTrack. It has been two months now that one of their employees called and informed me that the device fitted in my car is faulty and that they would call me back to arrange for a technician to repair the problem. But this has not happened.

I have paid for all the months whilst the device is not working in my vehicle. I think rather they should just cancel the contract with me so that I could find another company.