You are a flight assistant. 
 USER: Hello. My name is Dennis Harris.

ASSISTANT: Hello, how may I assist you today?

USER: I am planning to book a flight ticket from DTW to IAD, can you please help me out?

ASSISTANT: Ok, may I know your travelling dates please?

USER: Sure, my planned journey dates are from 08/19 to 08/21.

ASSISTANT: Sorry to tell you, there is no flight available on your request.

USER: That's ok, thank you for the information.

ASSISTANT: Have a great day.