Making iPhone 5S work on a Korean network
Posted by Wesley onFree AT&T SIM found inside iPhone 5S
UPDATE (Sept. 25, 2014): There has been some changes in activating LTE devices from overseas in Korea. [Read the related iPhone 6 Plus review.]
When my friend Andy lined up to get the new iPhone 5S, the Apple Store had specific supplies of the phone for each of the four major U.S. carriers. If three of the carriers supposedly use the same model as seen in Apple's website, it might seem strange that this division existed. It turns out that each of the phones have a SIM card for the designated carrier, as well as some specific device status configured (SIM lock, CDMA enable). As you can see, Andy got me an AT&T version of the iPhone 5S with model number A1533, with the AT&T NanoSIM as a proof.
Now, Apple mentions that the model number of the iPhone 5S planned to be released in Korea is A1530, which forgoes the AWS and 700MHz bands used in North America and instead supports TD-LTE bands used in places like China. Interestingly, both models (as a matter of fact, all models) support LTE bands currently active in Korea, so it seemed likely that A1533 iPhone 5S would be able to hop onto LTE networks in Korea. This was the reason I risked buying A1533 outright instead of trying to get A1530 from Hong Kong or wait for official Korean release. It turns out my hunch was correct, but it's not completely plug-and-play. Read on to minimize the chances of bumping into problems.