You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: My name is Karen Smith. I would like to change an existing reservation where my appointment with our doctor got changed.

ASSISTANT: Sure, may I know your name? Ok, please wait a minute.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no active reservation found under your name in our records.

USER: No issues,  thank you for the information.

ASSISTANT: Most welcome.