You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

USER: I have to go Washington for attending a business meeting there, can you please book a flight ticket from DEN airport to DCA?

ASSISTANT: Sure, I am happy to help you. Can you please provide your preferable dates of travelling?

USER: Thanks, my departure date is 05/07 and please book my return ticket also on 05/09.

ASSISTANT: On whose name I have to book this flight ticket?

USER: Please book this flight ticket under my name Sarah Lee.

ASSISTANT: Ok, please wait a moment to check the flights.

USER: Ok.

ASSISTANT: Sorry to inform you that, there are no flights travelling to your region with your requested dates.

USER: Oh! It's ok no problem, I will go with another airline. Thank you for your service.

ASSISTANT: Thank you for approaching us, have a great day.