In order to use Korean simcard in Korea, device should be unlocked. You
can check it through your current mobile carrier in your country before you
come to Korea.
Whereas a locked cell phone will only accept SIM cards from its current
provider, an unlocked cell phone will accept a SIM card from any service
provider. (This is very useful if you want to use your phone abroad, for
example.) To identify an unlocked cell phone, follow these steps.
Step 1
Turn off your cell phone, remove the battery cover and battery, then look
for the SIM card.
1) If you cannot find a SIM card in
the back, look for one in the side or top of the phone. It may be covered by a
small plastic flap. On some models, you will need to open the flap with a pin.
2) If your cell phone operates without a SIM card, it is a CDMA
(Code-Division Multiple Access) phone, as opposed to the more common GSM
(Global System for Mobile communication). CDMAs cannot be unlocked.
Step 2
Insert a
different service provider's SIM card into your phone and close it back up. For
example, if you have T Mobile, insert a Cingular
SIM card. The easiest way to do this is to borrow a phone from a friend.
Step 3
Turn on your phone.
Step 4
Try to access the phone book or make a call. If the phone functions
normally, you have an unlocked cell phone. If it says “Restricted,” “Contact
Service Provider,” etc. (in other words , doesn’t allow you to access your
phone book or make calls), you have a locked phone that won’t accept other SIM
cards from other providers.
- further more info :
http://www.wikihow.com/Find-Out-if-Your-Phone-Is-Unlocked