REPLACEMENT OF DEFECTIVE UNIT

A month ago my vehicle battery started giving problems & my vehicle wouldn't start. I took it to a Mercedes dealership who advised me that there is a problem with the tracking unit & it's draining my battery. I reported the problem to Matrix call centre who acknowledged the problem & indicated that the unit is old & needs to be replaced. I was then advised that the technical department will contact me to arrange the new installation. Three weeks pasted & I have not received a call/any feedback. I then contact the call centre again on 31.07.2015 & explained my situation once again. I was promised that it will be expedited to the Manager and he will give me a call before the end of the day. Guess what its the 04.08.2015 & still no call. I contacted the Matrix today again and explained the urgency of the problem as each week I am every other day I have to call for assistance to get my vehicle started. At the end of the day I my am taking money out of my pocket & paying for defective tracking unit. Furthermore my vehicles battery is weakening each day & soon it will be need to be replaced as at my expense again. I was told I will be called in the next few minutes but still no call.