Cartrack causing accidents

Worst place ever. Just over two years ago. Me and my wife was driving in my brand new car. Fitted with cartrack. When all of a sudden I can't find my brakes. Because they put the tracker behind my brake paddle. Luckily quik thinking helped me through it all. After that I called cartrack and canceled my contract. Very nicely. Now all of the sudden they won't stop calling me. Threatening me with saying there going toblack list me if I don't pay the R2000 that I owe them for canceling it. I lost my temper on the phone today. Sorry to be nasty if cartrack's C.E.O have the ***** please call me and we can have a talk man to man. Regards Arnold... ***