Are you sure they will give credits for the lower fare? Their web site states they will charge $75 a ticket to change the ticket, even if the rate is lower.
Edited to add: When I called her computer automatically took off the booking fee from the credit. She had to have a supervisor take the fee back off. Saved me $92!!! We worth the phone call!!!
So stupid question: How do I go about using this credit to pay for our checked bags?