You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I aid you today?

USER: I am John Garcia. I would like to change my existing reservation due to my scheduled examination dates has been postponed. Could you please help me in changing my reservation?

ASSISTANT: Ok, please hold a moment, let me check with your reservation and let you know.

USER: Ok.

ASSISTANT: Thanks for your time, sorry, unfortunately no reservation found with provided name.

USER: Ok, no issue.

ASSISTANT: Thank you for approaching us, have a great day ahead.

USER: Thank you for your information.