You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Please help me to book a flight ticket from DTW to DCA.

ASSISTANT: May I know your travel dates?

USER: June, 22 and June, 24 are my travel dates.

ASSISTANT: Do you have any connecting flight preferences?

USER: I need connecting flight.

ASSISTANT: May I know your name please?

USER: William Williams.

ASSISTANT: No flights found as per your preferences at the moment.

USER: That's ok, not a problem. Thank you for the information.

ASSISTANT: Thank you for choosing us.