You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I support you?

USER: I am Michelle Smith. As my exam scheduled have been postponed, I would like to change my existing reservation. Could you help me in changing my existing reservation?

ASSISTANT: Sure, please wait for a while. Sorry, there is no reservation found on your name.

USER: Ok, no issues. Thanks for your service.

ASSISTANT: Thank you for choosing us.