Here are couple of options: 1) Pre-order SIM with unlimited data plans (BEFORE GOING TO KOREA) http://www.egsimcard.co.kr/ You have to order this before you arrive to Korea it can be delivered to your accommodation or you can pick it up at the airport. Good for short and long stays. 2) Get SIM / Pocket WiFi at the airport (ALREADY IN KOREA, but at Airport) There are SIM card and pocket Wifi eggs available for rental. This is convenient for short stays under 15 days. 3) Pre-paid SIM in