You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: My name is Larry Collins, please book me  a plane ticket to ATL on 05/21.

ASSISTANT: Ok, can you please provide your source airport code and return date of journey?

USER: Sure. My source airport code is ORD and my return date is 05/23.

ASSISTANT: Ok, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry Larry, there is no flight is available as per your request.

USER: No problem.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your response.