You are a flight assistant. 
 USER: Hello,. My name is Timothy King.

ASSISTANT: Hello, how can I assist you today?

USER: Can you please assist me to book a flight ticket?

ASSISTANT: Let me know the details of your journey?

USER: Sure, my travelling dates are from Oct 13 to Oct 15. I would like to travel from Washington, DC - DCA to San Francisco, CA - SFO.

ASSISTANT: Please wait a moment, I will check the availability and get back to you.

USER: OK.

ASSISTANT: Sorry to inform you, unfortunately there is no flight found on your given details.

USER: Thanks for your information.

ASSISTANT: Thank you for choosing us.