You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Joshua Nelson here. I need to reach History Colorado Center in Denver to study about history of Denver. Can you please book a flight ticket from AUS to DEN?

ASSISTANT: Ok, please provide your complete airport codes and travelling dates.

USER: Sure, my travel dates are 12/14 and 12/16.

ASSISTANT: Sorry, no flights found as per your request.

USER: It's ok fine. Thank you for your information.

ASSISTANT: Thank you for choosing us.