You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I need to travel from DEN to EWR, can you help me?

ASSISTANT: Sure, on which dates would you like to travel?

USER: My trip dates are 05/20 and 05/22.

ASSISTANT: Is there any connection limit?

USER: I need a direct flight.

ASSISTANT: May I know your name?

USER: I am Ashley Young.

ASSISTANT: Do you have any other preferences?

USER: My return time must be in evening.

ASSISTANT: Ok, please wait for a while.

USER: Sorry, my return time must be in afternoon.

ASSISTANT: Ok. Sorry, there were no flights found with your given preferences.

USER: That's ok. Thank you for your help.

ASSISTANT: Thank you for choosing us.