You bought the tickets online as a Internet or Ding fare. Otherwise, yes, the previous person is correct. If you did buy online, it is very easy to cancel and rebook. Have two IE windows open and on one page have the cancel reservations page open and on the other page have the reservation page with the flight that you want open. Cancel your existing reservation first and then use the confirmation number from your canceled reservation to add the new reservation under the existing flight funds section. If you paid more then you will get a credit to use for future travel good for a year from your orginal reservation.