Poor service and attitude of call center personnel of cartrrack

I m very disappointed with the way they handled my complaint, I traded the car which was fitted with their tracker and phoned them to cancel it nobody ever told me about the letter of change of ownership that was about 6months ago then 2weeks ago they phoned me to say I owe them R600 I queried this and the consultant said he will come back to me but to my surprise yesterday morning I was phoned very early in the morning by a rude consultant who said I now owe R700.