You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you out?

USER: I am Brenda Wiliams. I would like to book a flight ticket from Las Vegas,NV-LAS to Boston, MA-BOS.

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: I want to depart on 12/14 and arrive on 12/16.

ASSISTANT: Sorry, there are no flights found.

USER: No problem, thank you for your help.

ASSISTANT: Thank you for reaching us.