You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: Can you please help me to book a flight from DFW to IAD?

ASSISTANT: Sure, may I know your trip dates?

USER: Sure, I want to travel on June 13 and need to return on June 15.

ASSISTANT: Do you need a single connecting flight?

USER: I need a flight with single connection.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: May I know your name?

USER: Robert Smith here.

ASSISTANT: Sorry, there are no flights available on your travelling dates.

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

ASSISTANT: Thank you for choosing us.