mattress with stain

Last November, I purchased a brand new Queen mattress for over $1000 in their Surrey store. I paid in full price. The delivery people were nice enough to set up the mattress and box. After two weeks of purchase, I tried to flip over the mattress as instructed from the sales person. I found there is a hugh stain with mattress on the other side. I was so mad; however, there is nothing they can do for me at all and I have to keep the unwanted mattress. A super disappointed customer.