You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I want to change my existing reservation, due to my exams has been postponed.

ASSISTANT: Sure, I am glad to help you.

USER: Thanks for accepting my request.

ASSISTANT: May I know your good name to proceed further?

USER: Sure, my name is Jessica Jackson.

ASSISTANT: There is no reservation found on your name in our database to change it.

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

ASSISTANT: Thank you for availing us.