You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Please help me to book a flight ticket from PHL to DCA.

ASSISTANT: Sure, please provide me with your preferable travel dates.

USER: My trip dates are from Dec, 16 to Dec, 18.

ASSISTANT: Do you have any preferences?

USER: I prefer a single connecting flight in business class.

ASSISTANT: Ok, is there any time concern?

USER: I need to depart in the afternoon.

ASSISTANT: May I know your name?

USER: I am David Perez.

ASSISTANT: Sorry, I did not find any flights for you.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for reaching us.