You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Can you please book a flight ticket from JFK to DTW?

ASSISTANT: Sure, I am here to help you. Can you please let me know your travel dates?

USER: Thank you. I have planned my travel dates as June 18 and June 20.

ASSISTANT: Ok, may I know your name?

USER: Sure, myself Mary Clark.

ASSISTANT: Do you have any class preference?

USER: I would prefer economy class.

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

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: You are welcome and thank you for choosing us.