You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

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

ASSISTANT: Sure, I am here to aid you.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: David Hall here.

ASSISTANT: Thanks for your name, please wait.

USER: Ok.

ASSISTANT: Thank you for waiting, no reservation was found on your name to change.

USER: That's ok, no problem.

ASSISTANT: Thank you for choosing us.

USER: Thank you.