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

ASSISTANT: Hello, how can I help you?

USER: I want to join the Brooklyn walking tour in DEN. Can you book me a ticket from IAH?

ASSISTANT: Sure, I am glad to help you.

USER: Thank you.

ASSISTANT: Please provide your planned travel dates to proceed further.

USER: I would start on Apr 15 and return on Apr 17.

ASSISTANT: May I know your preferred depart and return time?

USER: I need to return in the evening.

ASSISTANT: Do you prefer either economy or business class?

USER: I am okay with any class.

ASSISTANT: Ok, please let me know if you have any other requirement.

USER: I need 1 stop over.

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, we didn't find any flight for your journey details.

USER: That's Ok, thanks for your assistance.

ASSISTANT: Thank you.