Service Center Not Responding For Repair of microwave under warranty

I ve purchased an microwave oven of electrolux 4 months back after a month it stopped working. When i called customer care they are not responding.Now almost 3 months passed. When I called service center they always say that part is not available. Now i have called service center more than 15 times , they are always giving the same excuse..they are just giving careless attitude… Plz help me