You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, let me know your travel dates please?

USER: Ok, please book a ticket for the dates Sept 11 and Sept 13.

ASSISTANT: May I know your connection limit?

USER: My specification is to travel in a connecting flight.

ASSISTANT: Do you need any other preference?

USER: Yes, I need a flight which return timing is during afternoon.

ASSISTANT: Can I know your name please?

USER: My name is Rebecca Clark.

ASSISTANT: Sorry to inform you that there are no flight services available on your given details.

USER: Ok, that is not a problem. Thank you for assisting me.

ASSISTANT: Thanks for contacting us.