very bad service

I had my cars engine replaced exactly 2 weeks ago by Barloword Zambezi. Less than 150km later my car started leaking oil. I immediately went back to the garage. They looked and said that it was the side shaft leaking. The service manager said it will be covered by the warranty. It did not have any problems before the engine was replaced. Today I went to the McCarthy Hatfield btanch to get it replaced. At 4pm i was only informed that they do not have the necessary parts. And gave me a quote for over R1100. They say the warranty doesn't cover it. I am sick and tired of the quality of car I bought. I will never buy another Chevrolet again and I will tell all my family and friends to think twice before buying a Chevrolet.. The gearbox and engine was replaced in one year. How can that happen??