Over billing and not responding

My vehicle Tracker unit was apparently faulty. I was informed that a technician will come and repair/replace the unit if necessary at no cost to me.<br> After the unit was replaced I was billed for the replacement of the unit. I refused to pay for the new unit as it was made clear to me that there is no cost involved.<br> I paid my normal subscription as required and was informed that my subscription was suspended. <br> <br> As soon as the first time they invoiced me for the new unit, I logged onto my Tracker account and lodged a query. I am still waiting for a response.