You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I want to change my existing reservation which I have done before. Could you help me out of it?

ASSISTANT: Sure, can you provide your name for reservation done before.

USER: Myself Christine Smith.

ASSISTANT: Wait a moment Christine Smith.

USER: Ok.

ASSISTANT: Sorry to say, there is no active reservation found with your name.

USER: Ok, it's fine.Thank you for the information.

ASSISTANT: Thank you for approaching us.