You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you?

USER: I want to change my existing reservation, due to my exams has been postponed. Can you please aid me to change it?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your name to check the reservation status?

USER: Sure, please check my reservation on the name of Carol Brown.

ASSISTANT: Ok, please be on hold.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on your name in our airline database.

USER: Ok, thanks for your help.

ASSISTANT: Thank you for choosing us.