You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Kevin Clark, want to celebrate my birthday in Boston BOS. Can you check once is there any flight available from Denver DEN?

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

USER: My travel dates are from 08/28 to 08/30.

ASSISTANT: Please wait for a while, I will check the availability.

USER: Sure.

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

USER: That's fine, thank you.

ASSISTANT: Most welcome.