Is the below (from wiki) also true if it is after the first leg(s) of the trip have been taken?
"What are the change fees if I want to change a leg or multiple legs of the trip later?
$90 for changes after original booking. If there is an involuntary change because of flight schedules changing, there is no fee charged. Note that when you make a change, the taxes/fees associated with fuel, etc. may change. They may decrease or increase depending on the previous flight and the new flight. This is independent of the $90 rebooking fee. The $90 is flat regardless of how many of the segments you change. It is not $90 per changed segment."