You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Raymond Allen. Will you please assist me to book a flight ticket from IAD to LAS?

ASSISTANT: Sure Allen, can I know the travel dates please?

USER: Yes, my travelling dates are 11/25 and 11/27.

ASSISTANT: Ok, wait a moment.

USER: Ok, take your time.

ASSISTANT: Sorry, there are no flights available as per your request.

USER: Oh! It's ok, thank you for checking.

ASSISTANT: Thank you for approaching us.