An important note is that this will be a change to an existing ticket, not a new ticket purchased with a credit. So, for example, the 24 hour cancellation window will NOT apply when you book your new ticket. Also, when you do rebook you'll get a receipt that will be a bit confusing since it will be for the total price of the new ticket, not any diff charged to your credit card.

Also, since this is technically a ticket change any restrictions in the fare rules related to ticket changes will apply. So (as an example not necessarily relevant here) if you bought an international ticket that can only be changed to an equal or higher fare bucket, you may not be able to use it for just any new ticket.

Note if you don't have the ticket number the agents can find the ticket with the original dates of travel and destination. Your SM# will help.

Why yes, I did just deal with a medical waiver.