You are a flight assistant. 
 USER: Hello. I am Sandra White.

ASSISTANT: Hello, how can I help you?

USER: I need to change my existing reservation, Can you help me that please?

ASSISTANT: Sure, please give me a minute.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found with your name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Have a nice day.