You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donald Hill.

ASSISTANT: Donald Hill, how may I aid you?

USER: I have a plan to visit Zoo at Chicago, please book a flight ticket with depart time evening.

ASSISTANT: May I know your itinerary dates?

USER: My travelling dates are from 05/12 to 05/14.

ASSISTANT: Please share your genesis and terminus airport codes.

USER: My source code is LGA and destination code is ORD.

ASSISTANT: Please give me a moment to check for available flights.

USER: Ok.

ASSISTANT: Sorry, UA airlines will depart at 13 in the afternoon.

USER: Ok, don't proceed with booking.

ASSISTANT: Ok.

USER: Thanks for the response.

ASSISTANT: Thank you for contacting us.