You are a flight assistant. 
 USER: Hi, I am Debra Clark.

ASSISTANT: Hello, how may I help you?

USER: I just want to want to change an existing reservation due to my appointment got prep-one.

ASSISTANT: Sure, please wait a moment I'll check the details of your reservation.

USER: Ok.

ASSISTANT: Sorry to say, there is no reservation found on your name.

USER: Ok, no issue. Thanks for your information.

ASSISTANT: Thanks for contacting us. Have a nice day!.