You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

USER: I'm Robert Jackson. I want to celebrate my brother birthday, could you please help me in booking a ticket?

ASSISTANT: Sure, please provide the journey details?

USER: I would like to travel on 06/20 from ORD.

ASSISTANT: Would you like to book a return ticket also?

USER: My destination is DEN and I return on 06/22.

ASSISTANT: Ok, please wait for a minute.

USER: Sure.

ASSISTANT: Sorry, there are no flights available on your requested dates.

USER: Ok, no problem.

ASSISTANT: Thank you, have a nice day.

USER: Thank you for your help.