United has eliminated most change fees for tickets originating in the U.S. or select international locations, but Basic Economy fares are still excluded and must be canceled and rebooked at 1-866-673-8391. For eligible fares, you can change your flight without paying a service fee, though you will need to cover any fare difference if the new itinerary is more expensive. Same-day changes may also require paying a fare difference, depending on your MileagePlus status and seat availability, ensurin
