friend of mine ordered a part from a used dsm part distributor. they sent him the wrong side for the part he ordered. they told him to keep the incorrect one because they made a mistake. so i dont see why he'd have to ship the wrong one back at all. your mistake, you should be out the minor cost of the part. imo. as for paying for rentals etc, no. but i certainly understand his frustration on that point.
i work in retail, i listen to bitching all day from customers who are angry, never once have i hung up or walked off while they were talking to me.