You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: Please help me to book a flight ticket from IAD to DEN.

ASSISTANT: Sure, can you share your planned trip dates?

USER: Mar, 2 and Mar, 4 are my travel dates.

ASSISTANT: Do you have any connection limit?

USER: I would prefer single connection.

ASSISTANT: Is there any class preference?

USER: No, thanks.

ASSISTANT: Please forward your name.

USER: Raymond Parker here.

ASSISTANT: Sorry, there are no flights found on your specified trip dates.

USER: That's ok, thank you.

ASSISTANT: Thank you for availing us.