DOA laptop

My laptop was DOA when I received it on the 5th of this month. I returned it for repair and now the picture is really bad. I went through the picture adjustment procedure 3 times and it is somewhat better, but my old HP laptop is much better to the point I wish I had never bought this Dell. Not sure how to proceed, I guess I should call them. I heard I have 21 days to exchange it for a new one? It was gone for two weeks getting repaired which means I am paying new price for a refurbished laptop. I hope I can just get my money back. I made one payment already.