I was in South Korea in November 2022 for 10 days. Internet is very fast in Korea and it’s very cheap.Vodafone and Jio doesn’t work in Korea.I have Airtel mobile and it was working in South Korea as roaming and I was able to get all my OTP on my airtel mobile without any charges.I reached to Seoul International Airport and there people were selling SIM Card which will provide you unlimited internet for 10 days.Cost of SIM Card : 38,000 Won (1500 INR)