The cartrack unit which was installed on my vehicle stopped working almost two years back

The cartrack unit which was installed on my vehicle stopped working almost two years back. I reported the faulty unit to be repaired and on teo count the technician failed to pitch up to repair the device at my home address. Bearing in mind that the device is in a mini bus taxi it means i have had a loss on income on two counts where the technician failed to pitch up yet Cartrack still debits the account for a non functioning device they failed to come repair. After the two counts I resorted to not honour any repair bookings because they never pitch up and now cartrack reguse to cancel agreement, refuses to refund me and on top of it wants me to pay a cancelation fee for a non functioning unit.