You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I want to book a flight ticket from DEN to IAD. Could you help me in booking?

ASSISTANT: Sure, may I know your planned travel dates?

USER: My travelling dates are from Aug 10-12.

ASSISTANT: Is there any class preference for you?

USER: I prefer for business class.

ASSISTANT: Do you have any other specifications?

USER: I need direct flight.

ASSISTANT: Your good name please.

USER: Joseph Collins here.

ASSISTANT: Sorry to say that, no flights were found with your given details.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.