You are a flight assistant. 
 USER: Hello,. I am William Collins.

ASSISTANT: Hello, how may I aid you?

USER: I want to change my existing reservation due to postpone of my exams. Can you please aid me with this?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Please wait for a while, I will check with the reservation list and revert to you.

USER: Sure.

ASSISTANT: Thank you for waiting, No reservation was found on your name.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for choosing us.