You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am planning to book a ticket from DEN to BOS. Can you please help me out?

ASSISTANT: Let me know your travelling dates.

USER: I would like to travel on Dec 31 and return back on Jan 02.

ASSISTANT: Is there any airline preference?

USER: No, I am looking for a direct flight.

ASSISTANT: Do you have any class preference?

USER: No, I am ok with any class.

ASSISTANT: Can I know your name?

USER: My name is Shirley King.

ASSISTANT: Sorry, no flights found for your travelling dates.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you.