You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Sandra Jackson, want to travel from SFO to DCA. Please help me in booking my ticket.

ASSISTANT: Sure, may I know your trip dates?

USER: Sure, my trip dates are from 11/12 to 11/14.

ASSISTANT: Ok, please wait a minute.

USER: Sure.

ASSISTANT: Sorry, there is no flights available.

USER: It's ok, thank you.

ASSISTANT: Most welcome.