You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you for the day?

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

ASSISTANT: Sure, I am here to help you.

USER: Thank you for considering my request.

ASSISTANT: Can you please mention your name?

USER: Sure, my name is Kenneth Moore.

ASSISTANT: Sorry, no reservation found with your name.

USER: That's Ok, thanks for your information.

ASSISTANT: Thank you for choosing us.