And before anyone gets their panties in a bunch, this isn't fraud. This is legit. The CC company wants you to attempt to work it out with the merchant first which the OP has done and the merchant has been uncooperative. The customer is entitled to then call their CC and ask for a chargeback.
No, it's not legit...not in any way, shape, or form. OP ordered non-refundable tickets for the September party and got tickets for the September party. WDW fulfilled the order as requested and is within their rights to refuse an exchange - that does not constitute them being "uncooperative". They will provide full documentation of this to the credit card company as proof and the claim will be denied (this isn't their first rodeo as, sadly, many persons share your belief that credit card disputes are there for your entitlement, not to protect consumers from fraud).
OP has admitted the error was hers, not WDW's. I think your recommendation that she lie to take advantage of both WDW and the credit card company's policies is inappropriate and ill-advised (and probably against the rules of these forums as you are advising a "cheat")..
All that said, as others have recommended OP, call ticketing. At this early stage in the Halloween season, you can surely get the tickets switched without having to lose your principles or sense of ethics. I have read of several individuals who have been able to do so. Be polite, persistent, and if you get at CM who seems unable to help, ask for a supervisor or call back. I hope it all works out
