Kingsdown Body System Mattress Review

my husband and i went to mattress giant looking for a new mattress to help with our aches and pains. the kingsdown came highly recommended, even the sales woman (also the store manager) had one herself and loved it! we bought it. and it was very comfy. 1 month later we noticed the sagging. i went back to the store and the sales woman who had sold us the mattress insisted this was normal and to just rotate the mattress. so we did...now it sags in more than 2 areas. too late to exchange the mattress i get sent a "special kit"  to measure and photograph the areas on the mattress-1 1/2 inches, almost 2!! so, they have approved us to get another mattress, at a cost of $60-for delivery. great, now we are stuck getting another kingsdown and we have to pay for it! isn't it a bit odd they have these "kits" conveniently made up just for these instances? and seeing how it is their product that failed we are stuck paying for delivery?  i cant' say enough bad things about this experience. like everyone else, we should have stayed with our Serta.