Using your mobile phone in Korea

Before coming to Korea you might wonder whether you can use your mobile phone or not in this country. I bought a smartphone about one year ago. During this time I knew, that I would be going to Korea, so I got one that covers a lot of frequency bands. I chose the Samsung Galaxy S2; it can also operate with UMTS, which I read in advance is also used widely in Korea. I didn't want to get the Galaxy S3, because it was too big to fit into one of my hands; I also want it to fit into my smallest handbag (*ﾟｰﾟ)ゞ

While staying here I didn't get a Korean phone number. Most of the time I used open WIFIs to comunicate. There is one open WIFI operated by Olleh. This one doesn't allow you to use the Internet, but you can most of the time receive messages on Kakaotalk (doesn't work with the messengers Whatsapp or Line).

The Kakaotalk app is the number one choice for communication in Korea. You have to activate it with a text message, so it is helpful to install this app back in your home country. I didn't, but I am able to receive and send text messages in Korea. One short message, received in another country, won't make you poor, but remember, that you might not be able to receive it, depending on your mobile phone and your contract.
Kakaotalk allows you to send messages (including group chats) and call people (up to five people at the same time) for free. It is really essential here in Korea for communicating with your Korean friends. They are not very fond of writing e-mails  (¬､¬)

Source

If you want to get a Korean number you might hear that you need to have your Alien Registration Card first (it takes some weeks until you get it). But one French exchange student here got his number during his first week. So just take a Korean friend with you and you can at least try getting a number.

One German exchange student got his number from Olleh. It's similar to a prepaid card. He pays 10.000KRW (~8€) per month and can use the Internet and call people. This is as far as I know the cheapest option. But be careful. Use open WIFIs whenever you can, because Korea doesn't have a flat-rate system for Internet usage, like Germany has.

I am in Korea for about four months, and I managed to survive without a Korean phone number. Near coffee shops, fast food places and karaoke bars you can find open WIFIs. Sometimes, they are protected by a password, but just walk into the shop and ask for it.

You might end up not having a free WIFI in the CNU dormitory. So make sure to use your notebook for sharing the Internet (doesn't work on every machine) or bring an access point with you.