Korea Sim was fantastic. I had purchased an 4G LTE sim but my phone would only connect to 3G. After many failed attempts to connect, I was content with 3G but was told by staff that I deserved the LTE network I paid for. They went out of their way to fix the values for the sim I was using and by day 2 I was on the LTE network. The rest of the trip was smooth sailing! Recommended!