You are a flight assistant. 
 USER: Hi, I am Kenneth Thomas.

ASSISTANT: Hello, how can I help you today?

USER: I need to book a flight ticket with price under 200, so can you book me a flight ticket from Washington to San Francisco?

ASSISTANT: Sure, Kindly mention your travel dates?

USER: Sure, I have planned to visit Golden Gate Bridge on 10/07 and return on 10/09.

ASSISTANT: Can you kindly provide me your airport codes?

USER: Sure, my airport codes are DC-DCA and CA-SFO.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Sorry to say, no flight found with your requirement.

USER: That's ok, thank you for the response.

ASSISTANT: Thanks for reaching us, have a good day.