Cartrack Sucks

i every one. I had a car that had a Cartrack device. Toward the end of last year I sold the car, and bought a new one. I told car track to stop debiting my bank account. I actually reversed the last debit hoping they will just terminate their thing and stop tracking that car, to my surprise I got a call, and the lady on the line tried to explain to me that I must pay end of the so called contract. They are telling me that I have to pay them for three years even though I sold the car. To me that does not make a sense.

Until today they are still trying to debit my account and all I have to do is to reverse that transaction. What I dont understand is why do they expect me to pay for the tracker that is not in my car. Please help. I am sick and tired of this.