One problem that the OP had was the inability to book on the web, and having to call, and then being charged for making a reservation by telephone. Twice (out of a large number of reservations) I have had trouble using the United web site, but had the problem resolved by telephone. In those two cases they did not try to charge me for a phone reservation. I had called "web support" and not "reservations".

Does anyone know whether the standard NW policy is to charge or not charge in this situation?