Welcome to Korean technology. The same also happens with Korean Air. If you book on say, Delta, Delta has ZERO CONTROL over your reservation, nothing sticks, and even Korean Air can't do a dang thing for you because "delta controls the reservation." Sounds like the exact same thing here.

The ONLY way to do ANYTHING is to get an Asiana reservation confirmation number and use that in their system. Not the AC number, doesn't matter if you are a member of Asiana or not (but that helps the process lol)