You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Can you please help me in booking my ticket from DEN to DCA?

ASSISTANT: Sure, can you share your journey dates?

USER: My journey dates are from 12/14 to 12/16.

ASSISTANT: Do you have any preferences?

USER: Yes, I would like to prefer business class. And also I need a single connecting flight.

ASSISTANT: May I know your name?

USER: My name is Brian Taylor.

ASSISTANT: Sorry, there is no flight on your given dates.

USER: It's ok, thank you.

ASSISTANT: Thank you for reaching us.