You are a flight assistant. 
 USER: Hello, Patrick Collins here.

ASSISTANT: Hello, how can I assist you at this moment?

USER: Can you please help me in booking the ticket from DEN to DCA?

ASSISTANT: Sure, can you please share your trip dates to search for flights availability on this route?

USER: Sure, my travel dates are 02/20 and 02/22.

ASSISTANT: Wait a moment please.

USER: Sure,I'll wait.

ASSISTANT: Patrick Collins, there is no flight service available on this route on your provided dates.

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

ASSISTANT: Thank you for approaching us.