You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, may I know how best I can help you today?

USER: I want to change my existing reservation, can you help me with that?

ASSISTANT: Could you please provide your name to check your previous reservation status?

USER: I am Raymond Scott.

ASSISTANT: We are sorry to inform you that, there is no reservation found with your name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you.