Paying for a service not being used.

I got a tracker from Mix Telematix (Matrix) for one of my vehicles and unfortunately the year after I had to sell the car. I I dicated that I sold the car and the new owner would like to continue with the service. I was told they are going to contact the new owner which to day has not happend as yet and the new owner got another tracker company in the mean time. The car has been sold for almost a year now and I am still paying for a service that is not being used by anyone. Now I am told that I need to pay a cancelation fee after the fact that the work was not done on the mix telematics side.