You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Can you help me to book a flight ticket from DCA to OAK?

ASSISTANT: May I know your travel dates?

USER: My travel dates are 25 to 27 of Aug.

ASSISTANT: Do you prefer connecting flight?

USER: I need a direct flight.

ASSISTANT: Do you have any other specifications?

USER: I prefer to depart in the evening.

ASSISTANT: May I know your good name?

USER: I am Timothy Wilson.

ASSISTANT: Sorry, no flights are available in this route as per your requested dates.

USER: Oh! that very sad to hear, thank you.

ASSISTANT: Thank you for reaching us.