You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Nicholas Nelson.

ASSISTANT: How may I help you?

USER: I am planning to attend my sister's marriage in San Francisco, can you help me in booking the flight ticket?

ASSISTANT: May I know your airport codes?

USER: Sure, my source airport code is DCA and my destination airport code is SFO.

ASSISTANT: Please help me with your travel dates?

USER: Ok, my travel dates are from 02/02 to 02/04.

ASSISTANT: Sorry, there is no flight found basis on your details.

USER: Ok no problem, thank you for the information.

ASSISTANT: Thank you for reaching us.