You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I'm Nancy Green here. I want to travel for a city roundup trip at Washington, can you please book a ticket from DC-IAD to DC-DCA?

ASSISTANT: Sure, can you share your probable travelling dates?

USER: Sure, my preferable dates of journey are from 10/05 to 10/07.

ASSISTANT: Please allow me a moment to check for the availability of flight.

USER: Sure, please make sure that price is 200.

ASSISTANT: Sure. Nancy, I am sorry to inform you that there is no flight available at your requested dates.

USER: Ok, fine. Thank you for your service.

ASSISTANT: You are welcome. Thank you for contacting us.