Disappointing servicing communication

I am trying to communicate with somebody competent enough to understand the pathetic servicing I am receiving and the inferior quality or design of the C Class W205 model. My last query was about the brake pads, according to Century City Orbit, was checked but not replaced at the last service of 31 000km but 1 000km later, the warning for brake pads replacement appears. After many excuses from the dealer and silly responses from MBSA customer service, I again receive the following email: "Thank you for contacting Mercedes-Benz Customer Service. We would like to advise that we have certain parameters with regards to the replacement of brake pads. The Maintenance Plan only covers the replacement of brake pads approximately every 20 000km or more as this is the average life expectancy, therefore the dealer is unable to change brake pads when they are below minimum requirements" Yet when you purchase a Mercedes, of which this is my fourth, you are told that you will have peace of mind for six years or 100 000km. Why can I not reach some competent person in management regarding technical issues rather than communicating with some desk clerk at a call centre?