You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: Can you help me to book a flight from DCA to DEN?

ASSISTANT: May I know your travel Dates?

USER: My travel dates are Feb 28 and Mar 01.

ASSISTANT: Do you have any connecting limit preferences?

USER: I need a connecting flight.

ASSISTANT: Is there any other concern?

USER: I want to return in the afternoon time.

ASSISTANT: May I know your name please?

USER: Ronald Robinson here.

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

USER: Ok, thank you.

ASSISTANT: Thank you for choosing us.