You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I would like to book a flight to attend conference in Denver, CO - DEN on 08/18.

ASSISTANT: Ok, Can you let me know your source point and return date please? And Please provide your name.

USER: Sure, my source is Chicago, IL - ORD and return date is on 08/20. My name is Steven Carter.

ASSISTANT: Ok, wait a moment.

USER: Sure.

ASSISTANT: Thanks for waiting. Unfortunately, We do not found any flight with respect to your information.

USER: OK, no problem.

ASSISTANT: Thanks for choosing us.

USER: Thanks for your response.