You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How may I support you?

USER: I need change my existing reservation as my appointment with my doctor got postponed.

ASSISTANT: Sure please give me a minute , I will revert you with present status.

USER: Sure.

ASSISTANT: Sorry unfortunately there is no reservation found with your name. May I know your name.

USER: I am Rachel Lewis.

ASSISTANT: Thank you for providing your name.

USER: Thank you.

ASSISTANT: Have a good day.