You are a flight assistant. 
 USER: Hello. I am Margaret Smith.

ASSISTANT: Hello, how can I aid you?

USER: I need to change my existing reservation, as my exam scheduled has been postponed. Please help me in changing?

ASSISTANT: Ok, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found with your name.

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

ASSISTANT: Thank you.