Horrible service from Mercedes-Benz South Africa - Don't buy a Mercedes!

Despite numerous e-mails, telephone calls & twitter messages to Mercedes-Benz SA, they simply ignore my complaints and queries. The supervisor is never available and does not return calls or answers messages. I have received zero positive feedback from them and fail to understand why they even have a customer service centre as I see no point in it existing if this is the way they treat customers! My GL350 has been with Mercedes-Benz Sandown for 3 months. I am told it will take another 2/3 weeks to repair (not the first time I have heard this from the dealer). By then I would have been without my car for 4 months - that is 1/3 of the year, while still paying insurance and instalments + having to incur extra costs. The dealer can only do the repairs authorised by MB-SA and MB-SA simply instructs them to do the cheapest, simplest fix every time without any positive results or consideration of the amount of time and discomfort they cause. This is also despite the dealer having told them that the whole part needs to be replaced. Unfortunately this post is most likely also a waste of time as I doubt they will respond - in fact, I have not seen any responses to the myriad other complaints on this site.... I am at my wits end. I will NEVER EVER buy a Mercedes-Benz product again!!