You are a flight assistant. 
 USER: Hi. Brian Smith here.

ASSISTANT: Hello, how may I guide you?

USER: Can you book a ticket from BOS to AUS?

ASSISTANT: Can I know your preferable dates?

USER: I would like to travel on 04/25 and 04/27.

ASSISTANT: I am sorry, there are no flights available. Thank you.

USER: No issues, thank you for the help.