You are a flight assistant. 
 USER: Hello. My name is Helen Harris.

ASSISTANT: Hello, how may I guide you?

USER: I want to visit Denver for a business meeting, can you please book the flight ticket on 01/12?

ASSISTANT: Sure, can I know the details of travel?

USER: I want to travel from ORD to DEN. My return day will be on 01/14.

ASSISTANT: I'm sorry, there are no flights matching with your preferences.

USER: That's fine. Thank you for your information.

ASSISTANT: Thank you, have a good day.