You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Samuel Mitchell, want to book a ticket from ATL to DEN. Will you please help me?

ASSISTANT: Sure, may I know your trip dates?

USER: My trip dates are from 07/21 to 07/23.

ASSISTANT: For these dates, our agency is not providing any flight. So, sorry to say but there is no flight.

USER: It's ok, thank you for your help.

ASSISTANT: Most welcome.