Defective Mattress

Purchased a king size Sealy mattress & box spring set and after 3 days the mattress had terrible sagging.  Ashley sent a home inspector and they deemed it to be defective.  Went back to the store and upgraded to their top of the line Stearns & Foster mattress & box spring set.  Again after a few days the mattress was sagging like it was 20 years old.  They sent the same inspector and he deemed it to be defective.  I fought with Ashely customer service (which is horrible) and they agreed to issue me a refund and pick up the bed.  When they showed up they said they were only authorized to pick up the mattress, NOT the boxspring.  My wife called customer support and they explained that the box spring was not deemed to be defective and they would not take it back.  Fought for almost 2 months with customer service and the store representative and they will not take back the box spring even though I bought this as a SET.   DO NOT BUY A MATTRESS FROM ASHLEY FURNITURE.  THEY ARE DEFECTIVE AND THEY WILL NOT ISSUE YOU A REFUND!!!