You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Catherine Collins here.

ASSISTANT: How can I aid you now?

USER: I would like to depart in the afternoon time for my holiday trip to Denver. So can you book the flight ticket?

ASSISTANT: Sure, I am here to help you. Can you please provide me your source airport code?

USER: The airport codes are from LAS to DEN.

ASSISTANT: May I know your travelling dates for your trip?

USER: Yes, the trip dates are from Aug 05 to Aug 07.

ASSISTANT: Do you have any connection limit for your journey?

USER: I would prefer a stopover flight.

ASSISTANT: Let me know your class preference, that you prefer for the journey.

USER: No more preferences. You can search for the flight.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there are no flights available as per your specifications.

USER: Not a problem.

ASSISTANT: Thank you for opting us, have a good day.

USER: Thank you.