This was one of the first things I researched on once I decided upon signing up for the one-month language immersion programme in Seoul. While free Wi-Fi is readily available and easily tapped upon at most public places in Seoul, a more reliable form of access is more desirous given that I am likely to explore less touristy places during the month-long sojourn. I have written a considerably detailed account of how to go about applying for a prepaid plan in South Korea based on my personal experience:
There are two ways to register for a mobile phone prepaid plan: either with a passport, or with a certificate of Alien Registration, the latter which is available only to those who intend to stay in South Korea for more than 90 days. Since I was going to be in Seoul for about a month, I clearly fall into the former category. Even then, one cannot go to a local service provider immediately after arriving. There has to be a mandatory 3-working day time-lapse and apparently this is so to allow the immigration records to be input into the system. Say for example if you land on Saturday, please only attempt to visit the service provider on Thursday. Not any earlier. Trust me on this; we have tried.
First of all, ensure that you possess an unlocked mobile phone i.e. it will still operate if another SIM chip is inserted into it. Singaporeans need not worry because our mobile phones are all unlocked but if you hail from a country with locked mobile phones, do get it unlocked at your service provider before flying out. If this is not an option, then you should consider purchasing a used mobile phone at any mobile store in South Korea. There are a total of 3 service providers in South Korea: LG U+ (LGT), T (SKT) and Olleh (KT). It is not as simple as walking into any store of any of the 3 service providers because 1) they may not be able to understand your needs if you don’t speak enough Korean and 2) that particular shop may not be equipped to deal with foreigners. The safest bet is to visit a global store, and in my case I had mine done at KT’s Gwanghwamun Olleh Square after an afternoon cultural class ended at Gwanghwamun.
What really happens at the service provider is that you end up buying a USIM chip using your passport. My USIM chip for an iPhone 4 cost me 9,900₩. I think it was the same price for a friend’s Samsung S3. Reckon it shouldn’t vary too much for other make of mobile phones. And then together with the USIM the service staff would ask you for the plan you wish to buy along with the USIM chip. This is where things get a little confusing so it’s best to approach the service staff to check with them. But all in all, the calling and data plans are inexpensive. I paid 10,000₩ for the minimum calling plan (not expecting many calls) and 16,500₩ for a 1GB data plan. In total, I paid 36,000₩ and walked out of Olleh KT with a Korean mobile number (that till today I cannot remember).
I’m a rather heavy data plan-user. As of today (22 days after getting the plan), I am left with 182MB on my data plan and about 7 days more in Seoul. Thinking it wouldn’t be enough to tide me through the whole period, I walked into an Olleh KT store in Myeongdong yesterday when I went shopping, wanting to top up a little more to my data plan. The lady asked for my passport, and then after fiddling with the system she explained to me that I am only allowed to top up my data plan when I have completely depleted my remaining 182MB. I was perturbed and quite troubled because this was not explained to us clearly. Furthermore I’m spending the weekend in Gyeongju and expecting to use a lot of my data plan for navigation. What happens if my data plan runs out while I’m out visiting ancient tombs?
A USIM chip bought with a passport expires within 1-3 months depending on the plan you bought. Mine is expiring within a month, but if I top up the data plan, it should extend the lifespan of the line by 1 month or so. Not very clear about the regulations again. Just remember that it will absolutely not extend beyond 3 months.
This option of buying a USIM chip is not feasible for tourists visiting South Korea for a week or so. Just doesn’t make sense to apply for a line on the 4th day, only to fly home in another 4 days. In this case, it might be more logical to look into the option of renting a Wi-Fi router. This was what a friend did when he recently came over to Seoul for a holiday with his family.
[I understand that a few years back it wasn’t even possible for a foreigner who doesn’t have a certificate of Alien Registration to buy a USIM chip but this has changed recently. Given that South Korea is fast becoming more popular as a tourist destination, the regulations may change again in a couple of years’ time. So let’s just keep our fingers crossed.]
There is apparently a much easier way to purchase a prepaid SIM Card for use in Korea now. Please refer to this site for further details. Personally I have not tried out Evergreen SIM Card but from the description, it sounds pretty straight forward.