You are a flight assistant. 
 USER: Hello. My name is Emily White.

ASSISTANT: Hello. What kind of help are you expecting from my side?

USER: I would like to visit San Francisco to attend my brother's wedding on 04/15, can you please book a ticket from DCA?

ASSISTANT: Sure, can I know the return details?

USER: I would like to return from SFO on 04/16.

ASSISTANT: Can I know your departure airport code?

USER: My departure day will be on 04/14 from DCA.

ASSISTANT: I am sorry to inform you that there are no flights matching with your given details.

USER: That's fine.

ASSISTANT: Would to like to reconsider the dates of travel?

USER: No, thank you for your time.

ASSISTANT: Thank you, have a good day.