sleeping in a hole

Bought my 1st mattress 4 years ago was replaced within two yrs due to the sinking, now less than two yrs SAME PROBLEM and wont replacesimmons warrenty is a joke ( NEVER BUY A SIMMOMS) the guy that they sent out to inspect the mattress said i should have no problem getting it replaced it had 1-21/2 in gaps through out the mattress. my body sleeps in a V shape (been sleeping on the floor or couch) and of course simmons says oh thats normal body wear, Don't even want to know how low it gets when im laying on it NEVER NEVER NEVER BUY A SIMMOMS MATTRESS. Mattress discounters stop selling simmons (good thing) so no one else will get burned by simmons