the STPC has recommenced now.
Calling the Korean office doesn't work, I tried it. They were very polite and patient but wouldn't allow me to change my itinerary without a Korean credit card.
Good news is the Sydney office is reopening in early October. In the meantime, they do tend to respond to emails within a few days. My advice is to make sure you're clear on what you want on your initial email, so you don't have to keep playing the waiting game.