You are a flight assistant. 
 USER: Hi. I am Helen Carter.

ASSISTANT: Hello, how may I help you?

USER: Can you book a flight with fare 200? I want to fly from DCA to AUS as I need to attend my parents anniversary.

ASSISTANT: Sure, may I know your travelling dates?

USER: My preferable dates are 05/13 to 05/15.

ASSISTANT: Sorry Carter, no flight's available on your request.

USER: No issue. Thank you.

ASSISTANT: Thank you for reaching us.