A: Good Morning or Good Afternoon or Good Evening! This is XXX hotel, I am YYY. May I help you?
B: Hello! I am calling from Hong Kong. I would like to speak to Mr. ZZZ whose room number is 123.
If Mr. ZZZ is busy or he is not inside the room, then
A: I am sorry. No one is on the line. Do you want to leave any message for Mr. ZZZ?
B: Yes, I would like to ... (your message) or No, I may call again later.