How can I use my US-iPhone in South Korea? I have an iPhone 4S and I will be going to South Korea for a year for my 1st duty station in the army. What should I do? Can I get it unlocked or should I just by a phone over there? I need contact with my family.
Before buying a CDMA SIM in Korea, check that your iPhone 4s is 


a CDMA phone, and
unlocked


Calling stateside from South Korea using a Korea-issued SIM card may be expensive. You should consider getting iOS apps (e.g. Skype, WhatsApp) that relies on WiFi or data plan to communicate.