You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: Can you please help me with booking a flight ticket from BOS to DCA?

ASSISTANT: May I know your desired travel dates please?

USER: My travel dates are July 26 and 28.

ASSISTANT: Do you have any specifications?

USER: I would like to depart at afternoon.

ASSISTANT: May I know your name please?

USER: My name is Scott Wright.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: That's ok. Thank you.

ASSISTANT: Thank you for opting us.