The legacy carriers--United, US Airways, Delta, American--all charge a fee if you ticket your award by phone instead of online. Here's your guide to avoiding those phone fees:

United

United charges $25 per passenger if you book by phone. They will not waive this phone fee just because a booking could not be completed online. That's frustrating because many multi-city and free-oneway awards can't be booked online. They generate error messages despite being within the routing rules.

Here's how you avoid the phone fee with United:

First, search for and reserve any United flight.