You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: I want to book a flight ticket from DCA to SFO. Could you help me in booking?

ASSISTANT: Sure, I am here to help you. May I know your travel dates please?

USER: My travelling dates are form Feb 18 - 20.

ASSISTANT: Ok, do you have any specifications?

USER: I prefer for connecting flight.

ASSISTANT: Ok, hold on for a moment. Let me check the best available flight for you.

USER: Ok.

ASSISTANT: May I know your name please?

USER: Brenda Nelson.

ASSISTANT: Sorry Brenda Nelson, there are no flights available on your requested dates.

USER: That's ok, thank you.

ASSISTANT: Welcome, thank you for choosing us. Have a great day.