I would politely invite your dealer to pound some serious sand. I think the only thing you need to worry about is whether the dealer made a "mistake", as mistake is not a defense under the law (attorneys correct me on this if I am wrong). So if you tell the jackass to go F-himself, it's then up to him to prove he made a mistake and shouldn't be bound by the deal. All of that said, I'm sure it's just a ploy on their part to suck some more $$$ out of you. Sad to say, but I'll bet for every 10 people they call back with this line of BS, probably 2 or 3 just come right in and agree to the new deal.

This reminds me of when I bought my '93 Eagle Vision. A couple of months later I get a bill from the dealer for another $100 or so for the registration. I looked over my purchase agreement looking for language indicating I was obligated to pay anything after the deal, couldn't find it so I called them asking me to point me in that direction. The lady on the phone just got all huffy and essentially said "Well if you don't want to pay, don't!!". I said "It isn't that I don't want to pay, I just want you to tell me where I agreed to pay and then I'll pay, I just don't see it." She just got all huffy again and I didn't pay. Screw them.