You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am looking for a flight from DCA to SFO, can you please help me in booking?

ASSISTANT: Sure, can I know your name?

USER: Sure, my name is Elizabeth Campbell.

ASSISTANT: Thank you. May I know your travel dates?

USER: My travelling dates are Jan 25 and Jan 27.

ASSISTANT: Ok, do you have any preferences?

USER: I need a direct flight.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there is no direct flight available on your preferred travel dates.

USER: That's ok, thank you for checking.

ASSISTANT: You are welcome and thank you for choosing us.