You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you?

USER: I am planning to celebrate my birthday in San Francisco, so please book a flight ticket from DCA to SFO.

ASSISTANT: Sure, I am happy to help you. When are you willing to travel?

USER: I would like to fly on June 09, return on June 11.

ASSISTANT: May I know your good name?

USER: My name is Helen Harris.

ASSISTANT: Do you prefer any stopover in between journey?

USER: I need a connecting flight.

ASSISTANT: Is there any other specifications for you?

USER: I want business class flight ticket.

ASSISTANT: Sorry, no flights are available on your journey dates.

USER: Not an issue, thank you.

ASSISTANT: Thank you for availing us.