The alternate flights were available at the same fare the night I booked. I checked to be sure as soon as I realized my error. However, with no way to contact reservations and no option to change the booking online, I wasn't able to change the booking. I thought about cancelling and rebooking, but figured that might trigger a fraud alert on my credit card, in addition to maxing out my credit line.

The next morning, the fare was no longer available. It was available again the day after. Someone must have held a reservation and then cancelled it.

Next time, I will put a reservation on hold, rather than pay for it right away. That would give me time to ensure there is no error with the booking first.

Fare rules allow change, but at $200 per ticket, plus fare difference. That's a pretty steep expense for a family of four.