Booked a ticket to Vietnam but now have to change flight because of family emergency. Who to contact? Expedia or China Airlines?

Expedia.

contact the nearest China Airlines office

Contact China Airlines directly

Depending the conditions of the ticket you purchased you start with expedia. That there is or is not a fee was in the fine print you should have read at time of purchase.

Just because you want some other day does not mean there is an open seat or that day has the same fare.

If expedia will not help you then you try the Airline.

You can expect a fee to change. What that fee is will depend on the type of ticket your purchased. BARGAIN cheap , First Class.or something in the middle.

MANY cheap tickets are NO REFUND You just pay for and get a new ticket..

it was in your contract when you purchased the details of the answer.

Suggest you READ IT NOW.

You contact whoever you bought the ticket through, so if you got it using Expedia as your travel agent, contact them. If Expedia can't/won't help, then go to the airline, but they'll often tell you to talk to your travel agent anyways.

Every airline has a change fee unless you've paid for a class of fare that includes free changes, and those fares are usually a lot more expensive than the standard fares that most of us typically pay for.

contact the one you bought ticket from

Contact the airline.

What kind of ticket did you buy?.