Greeting is important in South Korea and There are different to say hello and that is what I learnt, so see them below
Hello – Annyeong Haseyo (in Hangul:안녕하세요) this is the standard way to say helll
Hello- Annyeong 안녕 is the informal way to say hello
Hello – Annyeong Hasibnikka (안녕하십니까) formal way to greet
Hello – Yeoboseyo (여보세요) used over phone calls