You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you at this moment?

USER: I am looking for a flight which returns to my location in the evening. Can you help me in booking a flight ticket to DTW from IAD?

ASSISTANT: Sure, please send your travelling dates.

USER: Sure, my travelling dates are Mar 25 and Mar 27.

ASSISTANT: Do you have any preferences?

USER: Yes, I prefer to have my booking with the normal-cost airline having a single connection.

ASSISTANT: May I know your name please?

USER: Sure, my name is Michael Roberts.

ASSISTANT: Sorry, there is no flight available with your given requirements.

USER: Not a problem, anyways thank you for the information.

ASSISTANT: You are welcome, have a nice day.