I learned '여보세요' as a way of saying 'Hello?' at the start of a conversation on the phone. However, I have heard it said in the middle of conversations too - sometimes when it seemed like people were arguing. What does '여보세요' mean in that situation? Could it be considered rude?
여보세요: From 여기 (yeogi) + 보다 (boda) + 세요 (seyo), literally “look here”.
It's usually used when you are not sure who you are talking to. For example:
Starting a conversation on the phone(You pick up the phone and you're not sure who you are talking to)
Ask someone's attention (이봐요! 여보세요! "maybe like Hey you!!!"). You may even talk loudly or shout to draw someone's attention. It makes your partner feel bad.
You are scared or you are happy or you want to greet someone who does not look at you. 여기요! 여보세요! 안녕하세요!
Just calling someone who doesn't pay any attention to you. 여보세요? 듣고 있어요?
The first usage is common but others may be used in special cases and not by everyone. Instead of using 여보세요! you can use 저기요 in some cases.
What you asked about is the second usage.
Adding to @Hanna and @Jake's great answers, when it is used in the middle of conversation, '여보세요' can express your disappointment, anger or surprise. It could be considered rude and impolite.
여보세요. 내가 뭐라고 그랬어요? (What did I say?) 왜 내 말을 안듣고 문제를 더 어렵게 만들어요? (Why did you make the matter worse without listening to my advice (words).)
In the sentence above, '여보세요' could be interpreted as
I can't believe what you just did. (expression of disappointment)
Did you listen to me or not? (expression of anger)
Don't you understand what I've just said? I can't believe you don't understand what I've said. (expression of surprise)
When you utter '여보세요' in a high pitch or sarcastic tone, it can express any of the above connotations or all of them combined. It all depends on your tone. It has a negative connotation when it is used in unfriendly tone.
여보세요. 왜 나한테 반말이예요? (Hey, why do you talk down to me?)
Also, it is used when you are addressing a person you don't know and you want to get their attention as follows:
여보세요. 여기 소주 한 병 더 주세요. (Hello (waiter or waitress), one more Soju here, please)
여보세요. 여기 (거기) 누구 없어요? (Hello, is anybody here (there)?) - It is used to ask if someone is in a place you are entering and the place is not familiar.
'여보세요' is commonly used to start a phone conversation, where it means hello. However the phrase has a totally different role when it's used in heated arguments where the phrase literally means 'you look here' and used to express the frustration or anger towards the other person. It's a bit rude expression.
Although it's not that common, '여보세요' also can used to get someone's attention in general. In this case, the meaning is similar to '잠깐만요', '실례합니다',