You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you?

USER: I'm Charles Hall. My business meeting has been postponed, so I would like to change my existing reservation. Can you please help me with that?

ASSISTANT: Sure, give me a minute?

USER: Sure.

ASSISTANT: I am sorry to say that there is no reservation found.As per your name.

USER: No problem. Thank you for checking.

ASSISTANT: Welcome.