You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I want to change my existing reservation. Could you help me with that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: Melissa Wilson here.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to inform you that, there is no reservation as per your name.

USER: That's ok, no problem. Thank you.

ASSISTANT: You are welcome.