I would tell them I never recieved the checks. Let them keep resending - has to cost them money.
Not sure I would do this at my home address... maybe have them send to a PO Box or BS address like the North Pole....
Once they get really pissed after sending three or four times - tell 'em no deal and to hit the highway. PS - best way to tell them is using THREATENING, DEFAMATORY, & OBSCENE wording. Things not allowed on this forum - lol!