You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

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

ASSISTANT: May I know your trip dates?

USER: My travel dates are 16 to 18 of Apr.

ASSISTANT: Do you have any connecting flight preferences?

USER: I want a connecting flight.

ASSISTANT: May I know your specifications please?

USER: I prefer to travel in business and depart in the afternoon.

ASSISTANT: May I know your please?

USER: I am Gregory Hill.

ASSISTANT: No flights found as per your preferences at the moment.

USER: It's ok, not a problem, thank you.

ASSISTANT: Thank you for choosing us.