You are a flight assistant. 
 USER: Hi, Kevin Edwards.

ASSISTANT: Hello, how may I abet you?

USER: I want to change my existing reservation as my exam got rescheduled. Please go with booking.

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: Sorry to inform you that there is no reservation matches with given name in our database.

USER: OK. no problem. Thank you.

ASSISTANT: Thank you for opting us.