✔ 最佳答案
You can buy the tel card from the counter at Incheon Airport, after you get out from the immigration gate. It's next to the information desk (where you can get a lot of maps and guide books).
3000Won and 5000 Won, 2 types for local calls. You can also get it in any convenience store in Seoul too. 5000 Won and 10000 Won for IDD (there should be some more types e.g. 20000 Won).
Remember : this card is for public tel. It's not a SIM card.
Usually when you see a public tel., just go in the convenience store next to it and you can buy the correct tel card for that telephone.
If you take your 3G mobile phone with you, you can use you own HK SIM card and the roaming service.