You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

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

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your good name please?

USER: My name is William Clark.

ASSISTANT: Please wait a minute.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry to inform you that there is no active reservation on your name to change.

USER: That's ok, thank you for your information.

ASSISTANT: Thank you for opting us.