My Tracking Unit hasn't been work for over a month!!!!!!!!!

on the 14th on May i received an SMS from cartrack informing me that my tracking unit is not responding, i called them immediately and they said that my unit last responded on the 18 of April. i made a booking to fix my tracking units which according to them would cost me R600, i agreeded and the consultant said the Germiston branch would contact me, today is the 17th and i havent heard anything from them yet. i have been driving all this time with a faulty unit! what is my car gets ******???? who's responsibility would that be. this is really poor service!!!!!!!!!!!!!