Mercedes Benz bad customer service

I'm Sam Sibusiso Nkombane currently residing in pretoria , the beginning of the year I took my wife's car for a major service a Mercedes Benz A220d I took it to Mercedes Benz melyn. After the service my wife drove the car for a week and it had a breakdown not having power to accelerate more while he was reroute to work at Ogies. I then called Mercedes lifestyle centre reporting a breakdown and they told me they will contact the nearest dealership, which for this case it was McCarthy Kunene witbank(Mercedes Benz) on arrival of the technician without doing diagnostic a saying my diesel is contaminated. It is then I said to the technician that is not correct I poured all 3 of my cars in Engen Silverlakes which are all diesel using 1 pump and all the cars are okay and fine exempt for the a class which was on service the previous week. We had an argument without reaching a consensus. We then concluded that the car will be towed to witbank. Before the two truck arrived I then enquired that I get a courtesy car from Mercedes benz as my car was still on warranty which the dealer refused point blank to give me. We argued until I told them I'll be taking my car to menlyn to which they agreed to provide a courtesy car, after informing McCarthy kunene about the development they then made a sudden turn to give me a courtesy car which we eventually took. Fast forward 2 weeks gone without any update from the dealership it is then we decided to go to witbank to enquire about the status upon arrival we were told that my car had contamination I then argued with the workshop manager and the dealership manager that was not true as the diagnostic was not carried by the technician when he arrived on site, I asked why would I buy doggy diesel for a car that I bought with 15kms on the clock and drove till it was on 95000 kms. And a consident is that my car was fine before I took on service and It broke after service. Upon our argument we agreed that ths diesel will be taken samples for analysis and before a sample can be taken all the stakeholders should be the including ourselves to witness as we could not trust ths dealer anymore. Fast forward the following monday we were not called by the dealership to come we wanted inacticipation of the call nothing came. Further 2 weeks down the line we have not received a call from the dealership it is then I decided to call again asking for feedback or update on our last meeting to my surprise the dealership took the sample for analysis without inviting us as previously agreed and I said I would not accept the results as we previously agreed to invite us so that we can witness as we know longer trust the dealer. It became clear that ths dealership could not be trusted anymore and I'm not trusting if they already poured water in my tank. It is then I further decided that to report the matter to Mercedes Benz south africa contact centre explained ths whole story and j was given a reference number of *** and I was promised feedback in 7 days. 7 days passed to 14 days until I then called asking for feedback ths consultant then said to me that ths dealership said my diesel is contaminated I said how can I trust the dealership who broke our agreement and said I'm not happy with their feedback and ths consultant told me that he escalated ths matter to his superiors till now no feedback. Yesterday I got a call from the courtesy car dealer saying I should bring back their car I said I'm not gonna bring back the car as I'm still waiting for Mercedes to fix my car as my car is on warranty I'm entitled to a courtesy car. So basically I need assistance as Mercedes Benz is not assisting as ths fault it's with them. Regards Sam ***