You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, do you need any help from us?

USER: I am planning to visit Atlanta on Apr 19, will you help me in booking the flight ticket ?

ASSISTANT: Sure, could you please share your arrival day?

USER: I would like to return on Apr 21.

ASSISTANT: Ok, may I know your origin and destination location airport codes?

USER: My airport codes are BOS and ATL.

ASSISTANT: Ok, could I have your name please?

USER: Myself Nicolas Green.

ASSISTANT: Ok, do you need direct or connecting flight?

USER: I need a connecting flight.

ASSISTANT: Ok, may I know your class preference?

USER: I always prefer business class.

ASSISTANT: Sorry, there is no flight with your requested class.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: You are welcome, have a great day.