You are a flight assistant. 
 USER: Hi, I am Joseph Young.

ASSISTANT: Hello, how may I help you?

USER: I need to book a ticket to DCA for watching the Jefferson Memorial Statue on 05/13.

ASSISTANT: Ok, let me know your source point and return date of your journey?

USER: I planned to return on 05/15 to SFO.

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

USER: Sure.

ASSISTANT: Thanks for waiting, sorry to inform that we have no flights regarding to your specifications.

USER: Thank you for your valuable information.

ASSISTANT: Thanks for contacting us. Have a nice day.