CARTRACK-submitting lower amounts so debit order can go through although stopped...and increase in premium without consul...

I fitted a cartrack device in my vehicle about a year ago and recently sold the vehicle.I contacted cartrack and enquired what the procedure is regarding the change of ownership.I was advised that i had to contniue paying for the device and if i have to cancel i would have to pay in a lump sum between R2500-R3000.I enquired about installing int another vehicle of mine ,i was told that it would cost another R350.My debit orders were going through although the car was sold until i discovered the policy suddenly increased by about R27 and a new amount debited without my consent.I was not contacted regarding the increase and was never advised of percentage increase during my initial contact with the sales department. I immediately cancelled the debit order.On doing so,without my consent,because they were not receiving payment for the full amount they deceivingly put through a smaller amount and with no funds in my account ,the debit was returned unpaid and i was charged R120 by fnb for unpaid debits.This has happened on several occasions.When contacted by the accounts department i asked the consultant to verify that i was informed of the increase and the new debit order which fell on deaf ears but im constantly receiving calls for payment.I called the Durban office this morning and was cut off 3 times.i continuously called but no one is answering their landline.My question is ,How do i reach you in case of an emergency.....