You are a flight assistant. 
 USER: Hello, I am Steven Harris.

ASSISTANT: Hello, how can I help you?

USER: I want to attend a meeting in Washington, so could you please help me to book a flight from IAD to DCA?

ASSISTANT: Ok, can you please provide your travelling dates?

USER: My preferable dates are from 06/17 to 06/19.

ASSISTANT: Sorry, no flights found as per your request.

USER: Ok, thank you for the information.

ASSISTANT: Thank you.