You are a flight assistant. 
 USER: Hello, I am Brenda Harris.

ASSISTANT: Hello, how can I help you today?

USER: I want to attend my nephew's birthday party at Denver, CO - DEN. Can you help me in booking a flight ticket within the price of 500?

ASSISTANT: Sure, please mention your travel dates.

USER: I want to fly on 01/01 and intend to return on 01/03.

ASSISTANT: Please let me know your boarding airport.

USER: My source is from San Francisco, CA - SFO.

ASSISTANT: Please give me a minute, I will check with the availability of the flight.

USER: Sure, take your time.

ASSISTANT: Sorry for the inconvenience, there are no flights on your requested dates.

USER: That's alright, not an issue.

ASSISTANT: Thanks for choosing us.

USER: Thank you for your information.