You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Michael Johnson. I need to attend business meeting with my clients at DFW, can you please help me to book a flight ticket from DEN?

ASSISTANT: Sure, may I know your travelling dates?

USER: Sure, my travel dates are June 20 and June 22.

ASSISTANT: Do you have any other specifications?

USER: My departing time is evening.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: There are no flights available on your travel dates.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for reaching us.