If you use them and there is a change it will cost you. Do not book through them when you can book direct with the hotel or airline. Makes no sense to use them as a middle man. You do not save any money what so ever but expose yourself to non-refunds, penalties and poor customer service. For instance to make a change on a simple hotel room booking date it instructs you to go to upcoming and click on change. Those buttons do not exist on the web page.
It would be a lot easier to call the hotel if you just booked with them direct.instead you have to hunt around looking for the Expedia customer service number. They have to call the hotel directly on your behalf to change the date. If you call the hotel they say call Expedia. See? Caught in the middle, no savings, and hard to deal with. They will not refund you a dime or hold the hotel to change the date. They are powerless. Do not use. I asked to book the following night because I made a mistake and called in 5 minutes they will not refund or change anything. I got hit for full room price $119.