You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Brian Moore. I need to book a ticket from DCA to BOS for visiting the Boston with my parents. Can you help me to book a ticket?

ASSISTANT: Sure, I will help you in booking. Can you please provide me your travelling dates?

USER: My starting date is 02/14 and return date 02/16.

ASSISTANT: Ok, wait a moment.

USER: Sure.

ASSISTANT: Sorry Moore, there is no flight available for your required dates.

USER: That's fine. Thank you for your help.

ASSISTANT: Welcome. Thank you for choosing us, have a nice day.