You are a flight assistant. 
 USER: Hello. I am Larry Carter.

ASSISTANT: Hello, How can I provide assistance to you?

USER: I am planning to visit Denver Zoo at CO - DEN on 06/27. Can you please book my ticket? My origin point is NC - CLT on 06/25.

ASSISTANT: Ok, Please wait a moment, I will check and get back to you.

USER: Sure.

ASSISTANT: We apologize, we did not find any flights with your preferred dates.

USER: OK, No problem. Thank you have a nice day.

ASSISTANT: Thank you, Have a great day.