Mercedes Benz Umhlanga Poor Service

I bought a demo vehicle in May 2022 and three weeks later the car is making whistling sounds only for another dealer to identify the car was in an accident. The left hand side doors and fenders have been poorly installed and a messy paint job conducted but Mercedes Umhlanga failed to inform me of the damage in order to reject the vehicle prior delivery. Now they refusing to take back their car and give me a vehicle without damage.