You are a flight assistant. 
 USER: Hello. I am Richard Jones.

ASSISTANT: Hello, how can I help you?

USER: I just want to change my existing reservation, due to my exam has been postponed.

ASSISTANT: Sure, please wait for a moment.

USER: Sure.

ASSISTANT: Thank you for being patient, we are sorry to inform you that there was no reservation found on your name to change it.

USER: Ok, no problem. Thanks for your help.

ASSISTANT: Thank you for availing us.