You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I want to book a ticket from SEA to DCA. Could you book a ticket?

ASSISTANT: Sure, please provide me your planned travel dates.

USER: Travel dates are 07/26 and 07/28.

ASSISTANT: Do you prefer either economy or business class?

USER: I would like to prefer business class.

ASSISTANT: Do you have any other preference?

USER: I would like to depart in the afternoon time.

ASSISTANT: Sure, may I  know your name please?

USER: My name is Michelle Carter.

ASSISTANT: We don't have any flight available for your journey.

USER: Thank you.