Appalling Customer Service from Mercedes Benz

I bought an A class Mercedes Benz in 2009 from NMI Durban. Whenever i serviced my vehicle i received poor updates from the service advisors and NMI was always late in picking me up to fetch my vehicle. When asked by their survey company to rate them i rated them poor. I then bought a C class Mercedes Benz in 2013 and when leaving my vehicle for a day service at 7.00am i then get the car at 18.00pm. The service advisors do not constantly keep you updated and are extremely poor at arranging the lift for you to pick up your vehicle. I waited an hour and a half on 13 May 2015 to be fetched to pick up my vehicle. I promised myself the last time i would buy Audi or BMW. NMI Durban seems to overbook vehicles and cannot cope with the workload and the the customers who pay an arm and a leg for their vehicle are not given calls to update them on their vehicle. They are not picked up timeously to collect their vehicles. On two occassions all the customers that were in the vehicle that picked us up complained about the poor service at NMR Durban. What on earth will it take for NMI Durban to improve their customer levels. I would also like to send the complaint to their supplier.