I goofed when I bought a ticket today - completely forgot that 9/1 is Labor Day. I had a bunch of vouchers to use up from re-faring prior trips, and I had no sooner left the airport than I realized I needed to change my ticket to travel a day later.

If I had booked just on my credit card I'd simply cancel and re-book. Since I used four vouchers and paid only about $60 on my card I assume that isn't an option. Should I be able to call in and change the dates without paying the change fee? If not, what happens in this situation?

Thanks in advance!