Depending on fare rules, a change fee applies to all non-refundable tickets. Any flights canceled on or before the scheduled date of travel will retain ticket value and can be credited against the price of another ticket.

Here are the rules:
If a reservation is canceled on/before the ticketed departure date, the value of the ticket may be applied toward future travel up to one year from the original issue date. Travel on the new ticket must be completed within one year of the original date of issue.
If any part of the ticket is unused after the ticketed departure date and the reservation has not been canceled, the ticket has no value.
Once the value of a non-refundable ticket has been applied towards the purchase of a new ticket, the original ticket is considered valueless.
Any difference in fare, if greater, must be collected. No refund is given for a decrease in fare (no residual value) and residual amount cannot be applied to the change fee. All non-refundable values remain non-refundable.