iPhone12 Pro Max (from AT&T, unlocked) The eSim was extremely easy to use as a data sim. I had the eSim QR code ready on a secondary device. When I arrived at Gimpo Airport 1) I immediately connected to the free Airport Wifi 2) went to the Cellular setting 3) Clicked the add eSim and by QR code 4) Scanned the QR code from my secondary device 5) Waited a few minutes for the phone to connect to the network (you may need to reset your phone but I didn’t have to) 6) I ensured that cellular data switching was off and that the new eSim was set as the primary data network, so it wouldn’t use my US phone line in the “Cellular Data” setting 7) enjoyed using the unlimited data! I was able to use the phone number provided with the QR code in the K-ETA and the Q-Code webpage. I did receive some random text messages with Bible versus, but I just ignored them. 10/10 would purchase again.