If you’re in need of fast and reliable 4G LTE + 100 minutes of outgoing calls and 100 outgoing texts (incoming is free), make sure to purchase in advance on their website or just find a booth at the airport terminal. Receiving and activating my SIM took only a couple minutes without any hiccups. I had the 10 day SIM Blue plan, which was cheaper than any of the competitors because of the online discount. I travelled mostly in Seoul and Busan but also went out into the countryside and I still had strong signal no matter where I went.Also, whenever I had a question or issue, the Facebook messenger customer service agent was very helpful.
I highly recommend this service when visiting Korea.
David Sang Hun Kim