I stayed in Korea for 4 months before and usually train tickets are decent enough to book at the counter. Maybe they were confused since not many people call in advance? Not really sure. But here, this might help you:
Directions
① Shuttle Bus (Dec. 8, 2006 – March 11, 2007):
- Fare: Roundtrip ₩30,000, Children ₩20,000 One-way ₩16,000, Children ₩11,000
- Route A: Shinchon (5:15, 8:20) Mapo (5:25, 8:30) Jamsil (5:50, 9:30)
- Route B: Sadang (5:20, 8:30) Novotel (5:30, 8:50) Yangjae (5:40, 9:00) Daechi (5:50, 9:10) Jamsil (6:20, 9:40)
- Route C: Nowon (5:10, 8:30) Junggye (5:15, 8:35) Seokgye (05:20) Jamsil (05:50, 09:30)
- Route D: Gangseo (5:00), Mokdong (5:10, 08:20), Omokgyo (5:15, 8:25), Mokdong Complex 5 (5:20, 8:30), Jamsil (5:50, 9:30),
- Route E: Hongjae (5:00), Jonggak (5:10) Hannam (5:20) Aupgujeong (5:30, 9:00) Jamsil (5:50, 9:30)
- Route F: Guro (5:00) Shindorim (5:05) Yeongdeungpo (5:10) Banpo (5:30) Jamsil (5:50)
- Route G: Gunja (5:20) Gwangnaru (5:25) Cheonho (5:30) Duncheonyeok (5:30) Jamsil (5:50)
※ The shuttle bus service schedule may change depending on the number of passengers at Jamsil.
② Train:
Take Cheongnyangni (Subway Line #1 Cheongnyangni Station) → to Gohan (travel time: 3 hours, 46 minutes, first train at 8:00, last train at 22:00) → Get off at Gohan Station and transfer onto Kangwon Land shuttle bus (10 minutes, 1 bus service every 1 hour) or take a taxi (takes about 10 minutes)
③ Bus:
East Seoul Bus Terminal (Subway Line #2 Gangbyeon Station) → Gohan Station (travel time 3 hours, first bus 6:10, last bus 23:00) → Get off at Gohan Station and take a taxi (10 minutes)