I booked ticks from SFO to BKK, used the onward leg and now I want to post pone the return journey by a week.
The tickets were booked using vayama thru skyscanner.
When I called cathay, the change fee and fare difference made it 4000-9000$.
(This is business class. Total coast of ticket was 4700$)
Cathay rep did suggested that I cancel my ticket and just book economy. She also put a hold on the ticket for 1day.
When I called Vayama, they said it there is no partial refund as I had already used up part of the ticket.
Does US DOT or any agency have a policy. Can vayama make up their own rules?

Also, what happens if I don't show up for the flight.
I am not planning to do this, but I do want to know.