Paint Discolourationof Oven type toaster

I just bought one oven type toaster white color on Oct14,2009.

When I used it for couple of times , its color at edge of glass door got discoloured and has become slightly yellow in color. Its looks very bad and should not have happened. This black and decker is considered to be best of it's kind but when I used it , i got dissappointed. I want to return it to shopkeeeper but he refused to take bak. Pls tell me what to do