You *don't* want to call Central Reservations (the 407-W-DISNEY number). There's nothing they can do to help you.
You'll want to call the WDW Ticket Office first thing tomorrow. (I think they keep hours close to 9-5, though you might want to try at 8) They handle all ticket fulfillments through the mail, and also have some latitude to bend rules.
I can't find the direct phone number at the moment, but you can call the Main Switchboard at 407-824-2222 and ask to be transferred to the Ticket Office (don't let them try and give you Central Reservations).
If you're lucky, they can snag the order before it's prepared for mailing and change it. But worst-case scenario would probably be that the original order is mailed out to you, and then when you get it they have you call back to arrange for an exchange.
-Rob