You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Paul Collins, I want to attend science exhibition held at Philadelphia, PA - PHL. Could you please help me in booking a ticket?

ASSISTANT: Ok, please  provide me your journey dates?

USER: My journey dates are on 12/18 and return on 12/20.

ASSISTANT: Ok, may I know your source point?

USER: Sure, my source airport is Chicago IL - ORD.

ASSISTANT: Ok, please wait.

USER: Ok.

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

USER: No problem.

ASSISTANT: Thank you for availing us.

USER: Thank you for your service.