Hi Min Jeong. I am assuming that since you work and live in Korea that you always answer the phone in Korean first, however if you hear the caller speak English I believe a simple, "Hello, this is [...name...], how may I help you?" would be fine. Perhaps after that you could follow up with, "Is there a particular person that you need to speak with?" and then forward the phone call out. Can you provide more information as to what a foreigner usually asks? Then maybe I can help form a sample conversation for you. -Jo

A practical thing to say is "I am very sorry. My English is very basic. Can you speak Korean?" If he says, "Sorry. No." Then you say, "Please hold. I'll get an English speaker to help you." Then you go and get an English speaker to help.

A professional way of answering the call would be [greeting] + [company name] + [your name]. For example: "Good morning, XYZ Advertising, Min Jeong speaking." "Hello, you've reached XYZ Advertising, this is Min Jeong." Your next question would be, "How may I help you?"