Denied a service

I brought my car for a service at this dealer, the service advisor by name of Wendy is telling me they won't service my car because i bought the car from Sandown motors(Sandton)/mercedes which is re-painted by the paint which is not Mercedes approved, now i am asked to do run around like a headless chicken do investigations with with the dealer where i bought a car which is their co-dealer. I am a customer, my car is due for a service, i need it to be serviced and i continue using it without any hustle. the issue they bringing upon me should be treated internally, unless of course they are trying to tell me that "I", myself re-painted the car which it won't end well if we going to take that direction.