You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,how can I support you?

USER: Please help me to change my existing reservation.

ASSISTANT: Sure, may I know your name?

USER: Yes, I am Patrick Smith.

ASSISTANT: OK,please wait for a moment?

USER: Sure.

ASSISTANT: Thank you for waiting, sorry to inform you that there is no reservation on your name.

USER: OK, no issue. Thanks for your responce.

ASSISTANT: Thank you for availing with us.