You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I would like to change my existing reservation, due to examination schedule postponed. Can you please help me?

ASSISTANT: Sure, may I know your good name?

USER: My name is Karen Smith.

ASSISTANT: Please wait for a moment.

USER: Sure, take your own time.

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

USER: No problem, thank you for checking.

ASSISTANT: Thank you for reaching us.