Cartrack trying to rob me.

Cartrack is trying to **** me, I paid them R600 to de-install the unit on the car I sold and re-install the unit on the car I just got, their technicians dragged their feet until WeBuyCars sold the car, I requested refund, instead of refunding me they ran another debit order for R600 making a total payment of R1200 for non-service. Has anyone experienced this kind of **** or is it normal practice?