You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: Sure, I am here to help you. May I know your name please?

USER: Thank you. Christopher Wilson here.

ASSISTANT: Ok, please stand by.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry we didn't find any reservation on your name.

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

ASSISTANT: Thank you for reaching us, have a nice day.