You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I help you?

USER: I am Mark Lewis, I want to change my existing reservation as my company meeting got postponed.

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

USER: Sure.

ASSISTANT: Sorry for the inconvenience, there is no reservation found on your name.

USER: Ok, no problem . Thank you for the information.

ASSISTANT: Thank you for approaching us. Have a nice day!.