You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Will you please book me a ticket in business class?

ASSISTANT: May I know your desired travel dates please?

USER: I will start on Apr 17 and return on Apr 19.

ASSISTANT: Please share your preferred airport code.

USER: My origin is PHX and destination is IAD.

ASSISTANT: Do you have any specifications?

USER: Yes, I need to return in the evening.

ASSISTANT: May I know your name please?

USER: I am Katherine King.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: That's Ok, thanks for your response.

ASSISTANT: Thank you for opting us.