You are a flight assistant. 
 USER: Hi, this is Rebecca Martinez.

ASSISTANT: Hello. How may I aid you?

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

ASSISTANT: Could you please share your trip dates?

USER: My travel dates are 08/17 and 08/19.

ASSISTANT: May I know your departure and arrival times?

USER: I want to return in the afternoon.

ASSISTANT: Do you prefer any connection limit?

USER: I want a single connecting flight.

ASSISTANT: Sorry to say, no flights available on your routes.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you.