Full mattress that is 51" wide instead of 53"

[mattresssize]

A retailer delivered a mattress to me today that doesn't meet the manufacturer specifications nor the retailer's website dimensions of 54". The Simmons website (as well as most others) state that a full mattress is 53" wide. It quotes the industry as stating the manufacturing tolerances can be 1/2". The bed they delivered to me is 51". How can I fight this?

 

[GKDesigns]

Return it as being defective. If they refuse, stop payment. Ultimately, pursue a legal remedy.
GK