Incheon International Airport has telecom and roaming counters from KT, LG U+ and SK Telecom in both Terminal 1 and Terminal 2. The practical point is that not every counter keeps the same hours. The airport's current directory lists selected 24-hour arrival-side counters, while many other counters operate limited daytime or evening hours.
At Terminal 1, the airport currently lists 24-hour KT, LG U+ and SK Telecom roaming counters near Arrival Hall F on the west side of the first floor. At Terminal 2, it lists 24-hour KT and LG U+ counters near Exit 4 and a 24-hour SK Telecom counter near Exit 7. Other carrier desks are also listed in departure and arrival areas with their own hours.
Use the airport directory to choose a counter in your actual terminal before walking across the building. If you need a specific prepaid SIM, eSIM, roaming package, device rental or foreign-card payment method, check the carrier's current product terms directly; the airport directory confirms the counters and hours but does not guarantee that every product is sold at every desk.
For a very late arrival, save the terminal and counter location before landing. If you already have an eSIM that can be activated without a physical visit, completing setup before the flight may avoid an airport stop, but activation and device compatibility depend on the provider.