Mercedes unavailability of Parts

My vehicle has been at Mercedes Benz Sandton for more than 4 months. I have been informed by the service and mangers of the dealership that the part has NO ETA. Furthermore Mercedes offered me a rental vehicle that i have to pay for and would not provide a courtesy car.

This is a frustration and an inconvenience by a Big Company such as Mercedes Benz. I am currently paying for a vehicle i don't have.