You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT: Ok, sure can I know your travelling dates please?

USER: My trip dates are Dec 11 and Dec 13.

ASSISTANT: May I know your name please?

USER: I am Barbara Martinez.

ASSISTANT: Do you have any connection limit?

USER: I need a connecting flight.

ASSISTANT: Do you have any requirement?

USER: I would like to return in the evening.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry, no flight.

USER: It's ok, thank you.

ASSISTANT: Thank you for reaching us.