somewhat related question...I am on TMO with a Note 4 - had it with me when in Manila/Tokyo/Seoul (in transit) back in January 2014. I have their "unlimited data plan" which when outside the USA/4G LTE, it dropps to 3G.
Worked like a charm in Japan, while in transit in Seoul it was good to...but Manila....psh, dialup is faster (not). Are the main/big cities atleast 3G in Korea as I'll have that Note 4 with me when I (hope to) travel to Seoul w/a friend in July next year....
TIA.