You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you?

USER: I want to fly to Denver on Jan 9th to attend a client meeting and I'll return within two days that is on Jan 11th. Could you please help me to book a flight ticket?

ASSISTANT: Sure, I will help you. Please send your airport codes.

USER: I would like to start my journey from IAD and my landing airport code is DEN.

ASSISTANT: Do you have any preferences?

USER: I prefer to fly with the business class for this time.

ASSISTANT: May I know your name please?

USER: I am Joshua Rodriguez.

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

USER: That's ok, I'll choose any alternative to reach my destination. Thank you for your information.

ASSISTANT: You are welcome, have a nice day.