You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I am Patrick Walker. I want to change my existing reservation due to postpone of my exam dates. Can you please help me with this?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait for a few minutes.

USER: Sure.

ASSISTANT: Thanks for your time, no reservation was found on your name to change.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us.