You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I am Catherine Thompson. I want to book a flight ticket to attend my nephew's birthday in Denver. Could you help me in booking a flight ticket with a price limit of 200?

ASSISTANT: Sure, please provide your journey points?

USER: My source from CA - LAX and destination to CO - DEN.

ASSISTANT: Please assign your dates of trip?

USER: My departure is 06/19 and return date on 06/21.

ASSISTANT: Sorry, no flights available on given dates.

USER: Not an issue. Thanks for your help.

ASSISTANT: Thank you for opting us.