I am trying to book my flight from SFO to ICN and am debating between 2 airlines: Asiana or Singapore. I mainly want to book with an airline that allows me to change the date of my returning flight at minimal to no costs.

Currently...the fares are as follows:
Singapore RT = $926
Asiana RT = $895

Singapore says that the rebooking fee is only $20 + fare difference, which I think is pretty darn good since I believe Asiana charges $100 + fare difference. However, I'm also reading that in order to change your Singapore flight, you would have to call the Singapore reps, which apparently costs an extra $50.

So I just wanted to know if there are actually hidden fees a part from the $20 rebooking fee?