You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I am Larry Clark. I want to change my existing reservation due to postpone of my exams. Can you please help me with this?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to say that, no reservation was found with your good name.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for reaching us.