Replacement iPhone shipped to Korea - customs charges??

HI there, I recently had a problem with my iPhone 6 (under warranty) and called apple for service. I live in Korea and the phone was bought in the U.S., so I would usually have to go back there for service but Apple agreed to send a replacement for me to exchange. However they can only send to the U.S. so they said a friend will have to forward it on. My question is, when my friend sends it over here, am I likely to get stung with import duty at customs, even though it is a replacement? The paperwork from Apple should say it's a replacement and I'm not paying anything for it...

any ideas?

thanks