shoddy service from Mercedes-Benz

In September 2019, I took my Mercedes-Benz B200 Turbo sedan for a check up. The technicians discovered that the exhaust system was faulty, and ordered the part needed from Mercedes-Benz, Germany. It is now a year later, and I have not yet heard from them about the missing part. I have even been told to contact Mercedes-Benz Head office myself to inquire about when I could expect the part to arrive. I am so disgusted with Mercedes-Benz shoddy service! If this is the way they treat their customers, I'll think twice before buying another vehicle from them!!