$1800 Beautyrest mattress has two sagging trenches

We bought an $1800 Beautyrest World Class mattress and box springs 3 years ago (2008). It now has two trenches that sag where we lay. It is the type that cannot be turned over. Although we turn the mattress around, foot to head, nothing has helped to reduce the sagging.

I can't find the paperwork to be able to contact the manufacturer for warranty.

The mattress and box spring measures 25" tall, so tall that we barely can get in and out of bed. Bed frame is all the way down as far as it will go. So adding another inch placing a board in between box spring and mattress will make it harder to get in and out of bed.

We thought we were buying a quality mattress but it has turned out to be worse than our old mattress that we only paid $300 for. We will never buy another Beautyrest mattress. Brand name is all hype.