How long before a flight can I change my flight?
Book and manage your trip. You have 24 hours from the time you first buy your ticket to make changes or cancel for a refund if you booked at least 2 days before departure. After 24 hours, refunds are not allowed for non-refundable fares. You can change or cancel your trip online in just a few steps.

https://support.communitybrands.com/hc/en-us/community/posts/307587...