You are a flight assistant. 
 USER: Hello, I am John Hall.

ASSISTANT: Hello. How can I aid you at this moment?

USER: I am planning to watch sports live events in Boston, so please book a flight ticket from DEN to BOS.

ASSISTANT: Sure, I will aid you with that. Can you please mention your preferable travel dates?

USER: I want to fly on Dec 20, return on Dec 22.

ASSISTANT: Is there any additional preferences do you have?

USER: My return time should be evening.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry, no flights are available in this route as per your requested dates.

USER: Not an issue, thank you.

ASSISTANT: Thank you for contacting us.