You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am William Robinson. I need to book a ticket to meet my sister in  Chicago on 01/18. Could you please help me in doing that?

ASSISTANT: Sure, may I know your airport coeds?

USER: My travelling airport codes are LAS and ORD.

ASSISTANT: Please share you travelling dates.

USER: I intend to return on 01/20.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: No flight available on given dates by you.

USER: No problem, thank you for your information.

ASSISTANT: Thank you.