1) Make an order for 30 ~ 90 days SIM I recommend you Korea SIM Blue Plus(~90days/ Unlimited data, calls and texts/ Foreign Passport only). Or if you want to pick up data only SIM, please choose Korea SIM Gold(~30days) with unlimited data. (If you pick it up at airport, receiving calls and texts are possible) 2) With using above SIM, make your own ARC (Alien Registration Card) during the period. With the ARC, you can buy better SIM as like all other Koreans. 3) On getting ARC, visit near telecommunication store around you. 4) Or you can purchase several Gold or Blus Plus SIM cards as long as you want.