You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER:  As I am a scientist, I want to attend science festival with my students at Washington.

ASSISTANT: Can you please share on what dates you are willing to travel?

USER: Can you help me to book a ticket from SFO to DCA?

ASSISTANT: Can you please provide your travelling dates?

USER: My trip dates are 05/27 and 05/29.

ASSISTANT: Do you have any other requirements that you are looking for?

USER: I need only direct flight.

ASSISTANT: May I know your name to proceed further?

USER: Thomas Walker here.

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

USER: No problem, Thanks for the information.

ASSISTANT: Thank you for contacting us, have a nice day.