You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

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

ASSISTANT: Sure, may I know your trip dates?

USER: Dec, 31 and Jan, 2 are my trip dates.

ASSISTANT: Do you need any way station in your journey?

USER: Yes, I need a stopover.

ASSISTANT: Do you have any other requirements?

USER: No, thanks.

ASSISTANT: May I know your name please?

USER: Samuel Parker here.

ASSISTANT: Sorry to inform you that, there are no flights available with your requirements.

USER: That's ok, thank you for the information.

ASSISTANT: Thank you for choosing us.