Call CA and tell them you messed up and booked a day earlier then you ment to. Last year I booked 7 tickets to return a day before a cruise was over. CA did a warm transfer to reservations and they took care of me - no change fees. They didn't even know my status at the time so that was not a factor. To pay $700 in change fees would have been a real downer...

I did call about 1-2 weeks afer making the reservation and about 6 months before the flights.

Good luck...it's worth a try.