You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I need to book a ticket from DCA to SFO. Could you book a ticket?

ASSISTANT: Sure, may I know your name please?

USER: I am Elizabeth Edwards.

ASSISTANT: May I know on which dates your willing to travel?

USER: Travel dates are from Apr, 6 to Apr, 8.

ASSISTANT: Is there any specific class preference for you?

USER: I prefer business class ticket.

ASSISTANT: Do you have any other specifications please?

USER: I would like to depart in the afternoon.

ASSISTANT: Sorry Edwards, there is no flight found as per your travelling details.

USER: Thank you.

ASSISTANT: Thank you for reaching us.