Southwest Airlines offers eligible passengers free same-day flight changes, but there is a catch if you paid separately for your seat. Asking an airport agent to make the change can leave that seat purchase nonrefundable, while making the change through the app, website, or telephone receives different treatment. Apparently, how you change your flight now matters almost as much as which flight you choose.

Southwest’s Same-Day Flight Changes Come With A Seat-Fee Trap

View From The Wing highlights a peculiar provision in Southwest’s seat refund and exchange policy .

For passengers who separately purchased a seat on their original flight, Southwest explicitly states:

“Same-day change requested at the airport: Seat purchased on original flight is non-refundable.”

But complete that same-day change through Southwest.com, the Southwest app, or by telephone, and the rules provide a way to apply the original seat payment toward a replacement or receive a refund when buying a more expensive seat.

You could be…