I believe that if you made the booking via Orbitz, then only Orbitz can make changes to your reservation.. which also means that you must pay whatever price difference/fees they quote you.. regardless of what the airline says. I had a previous run-in with Travelocity, who claimed the only other fare available was an extra $160, despite United's claim that there was a cheaper fare.. since then, I have always gone through the ual.com website.

I'm not sure how this works in the computer system.. does the booking agent "lock" the reservation or something? Or does this exist strictly in policy and not actual system architecture?