Paying for Nothing

I had a Tracker unit installed in my old car, not knowing that it was a 3 year contract( Nobody mentioned it). I sold the car to someone else with the understanding that his going to carry on with the premiums. I notified Tracker in give them the new owner's number. He agree to even upgrade the unit with them and they said that they spoke to him. After 6 month they started sending threatening SMS to let me know that I owe them money. They want me to pay for a unit that I'm not using or have anymore, while they still get payment from the new owner. Now I have to pay R1050 to buy out my contract. I were paying for six month for something that is of no use to me. I wrote numerous letters to offices to no avail. When I finally spoke to someone(Sade Lovedale)<br> she arrogantly said there is nothing she can do and it is my responsibility to read the T's&C's.