You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I would like to attend for a seminar in DCA. Can you please help me to book a flight from BOS?

ASSISTANT: Sure, can you please share your travel dates?

USER: Sure, my travelling dates are from Dec 23 to Dec 25.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: May I know your connection limit?

USER: I need a flight with single connection.

ASSISTANT: Do you have any other specification that you are looking for?

USER: Yes, I prefer to travel in normal-cost airline.

ASSISTANT: May I know your name to proceed further?

USER: Sure, my name is Kevin Smith.

ASSISTANT: Kevin Smith, I am sorry to inform you that there is no flight available at your request.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Thank you for contacting us.