Hello, This is Harum =)
I haven't post in English for a while. I found out someone in English searched "How to initialize KT usim" so this is the posting for that question. So First of all, I searched for all the internet and other stuff. Here We go!
1. It must be open to traffic.
2. put your usim into the device.
3. In the waiting display, you should press registration of number. It looks like "번호등록" in Korean. (just in case, English doesn't appear)
If you can't automatically register 3G phone. Take this step.
1. Press call button(the button to call someone)
2. press *147359*682 and then press your number. After this, press Enter (It looks like "확인" in Korean)
if this number doesn't work put your usim out and turn off a min then on again. and take the first step for 3~4 times. If this doesn't work, you should go to KT shop to fix (there are many problems you may not fix by yourself, so I recommend to go KT shop)
3. It will display "waiting for registration of number" then restart the phone.
4. DONE!
[출처] [SKT/ KT/ LGT 나밍 방법]각 통신사 유심등록 하는법|작성자 후레쉬