You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

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

ASSISTANT: Sure, I am very happy to help you with that. Can I know your name to check your recent reservation.

USER: Sure, please check my reservation on the name of Rebecca Nelson.

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

USER: Ok, thanks for your information.

ASSISTANT: Thank you for opting us.