Simmons Mattress Sold me a defective mattress Long Beach California

I purchased a simmons pillow top mattress through HSN received it, First thing I noticed was some of the tags were cut off,I went ahead and had them install the box spring and mattress on my bed frame.I had it for year and 3 months and it sags in the middle to were two people uncomfortable to sleep,They sent a inspector out he checked the frame said it was ok then he took some pictures and measurements and told me there is something going on here(his words) He turned in his report and one week later I received a denied notice stating that the measurements were within tolerance and there was to stains on the mattress.I feel this is very unfair for a mattress that is a little over a year old to do this and further more what does the stains have to do with it.

Gary
Long Beach, California
U.S.A.