Mercedes Midrand conning clients big time

I booked my car for service on the 9th Dec at Grand Central Midrand. My car is still under Motorplan. The service advisor turned me back when I got to the dealership saying even though my car is under Motor Plan, Grand Central cannot service my car as it has already been to a Mercedes dealership 5 times. He showed me the cars history and said I must go back and book again and ask for quote for which he estimated at R8000. Later I called Mercedes Head Office and was told my car is under Motor Plan and I can take it to any dealership free of charge countless times during the Motor Plan period. I have since got the car serviced at Mercedes Fountains PTA. Grand Central has lost me and anyone that I know who owns a Mercedes.