Have booked two "saver" tickets for 25K RT and want to change one of the legs to first class. There is F class available at 25K, so it's another 12,500 miles each. That's fine, but is there also a fee?

The rules don't mention changes to class of "service":

1. Changes must be requested by contacting US Airways Reservations and are subject to award seat availability
2. Changes to the point of origin, destination, or stopover are permitted, provided the new itinerary is still within the valid travel areas allowed by the original award. A $100 service fee will be charged for any such changes.
3. Changes to flight times and/or dates are permitted at no charge. This includes changes to connecting points, provided origin and destination remain the same.


Thanks!