Just fyi, there are two apps that might be useful.
One is
Subway Korea. I have put a link the iOS version, but you can find an Android version as well. The app has a setting for English. This will cover just about every subway station in Korea.
Another app is
Korail Talk. This will allow you to book tickets on Korail, including KTX tickets. There is an English setting. Link is also for iOS but I am sure there other version as well.