Having quite an issue finding an agent who knows how to do this at the 1K desk. I am trying to do it not for the seat assignment, but rather the UDU on the domestic leg. The reps at the United Clubs have been universally helpless, but I don't expect them to be any better because they only handle same-day flights.

So far, I've gotten three different answers:

1. It's impossible because you are traveling on the outbound leg today and we can't make changes the same day you are flying on a ticket (even though the return is several days from now)
2. It's impossible because it is marketed as a direct flight and there's nothing we can do,
3. My favorite, after 40 minutes, was an agent and her Service Director who tried, but because the itinerary "wouldn't save" after 30 minutes of typing, said the only way was to book me on a different connecting flight and charging me the $250 international change fee.

So I'll keep calling back until my battery dies, but this is quite yukky.