I used to be an exchanging student here, and I had been using chingumobile since then. And this time, I still got a sim card comes with an unlimited data from chingumobile when I travel to SK. The reason why I keep chosing chingumobile is that the price is cheap, and the service is good as well. No matter you are simply a tourist or staying SK for a long term, I recommend you to take chingumobile as the priority.