I had discount business class ticket SEA-BKK // SGN-SEA. I wanted to change return but did not know exactly when I will be returning. The agent suggested to cancel return and rebook later.

So far great.... I​​​​​​ assumed that I would be able to rebook return using historical fares (so I just pay change fee as long as original booking class and original ticket rules apply).

Not so! When I called to rebook the agent spent about half hour with rate desk calculating remaining value of return ticket and applied it to brand new one way ticket, which was of course way too expensive.

Eventually I rebooked into one way coach and got e-cert for remaining value. Not bad, but I was hoping for buisiness with change fee.

Lesson learned:

- Changing return flight => applies historical roundtrip fares (even if you change routing or return from different city)

- Cancelling return and rebooking later => aplpies new one way fare.