You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Brian Wilson here.

ASSISTANT: Brian Wilson, how can I aid you today?

USER: Can you please help me in booking a flight ticket from SFO to JFK?

ASSISTANT: Sure, I am here to help you. May I know your travel dates please?

USER: Sure, my travel dates are from May 18 to May 20.

ASSISTANT: Ok, hold on for a moment. Let me check the best flight for you. I found a flight for you with Delta airline and it costs you 200. Shall I proceed?

USER: Please make sure that my return time must  be in the evening.

ASSISTANT: Sorry Brian Wilson, there are no flights available on evening time in those routes. Sorry for the inconvenience provided.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Welcome, thank you for choosing us. Have a great day.