Tank Assembly problems of the 2003 Suzuki XL7

I bought NY 2003 Suzuki Xl7 in March 2006 . I was putting gas in when the fuel tank door fell off. Before the warranty was up. I called the dealership he said it was not covered but could get me a new one and paint it for about $100. 00. Why I just bought it less than 4 weeks ago used but I didn't expect it. I was shocked and so disappointed because I really like this vehicle.