You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Richard Perez, want to travel from BOS to IAD. Please help me in booking my ticket.

ASSISTANT: Sure, may I know your trip dates please?

USER: Sure, my travelling dates are from 05/15 to 05/17.

ASSISTANT: Sorry, there is no flight available as per your request.

USER: It's ok, thank you.

ASSISTANT: My pleasure.