You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Brandon Williams. Please book me a ticket from PHL to DCA to meet my family.

ASSISTANT: May I know your desired travel dates please?

USER: I would like to leave on 03/18 and return on 03/20.

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

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.