You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am very happy to change my existing reservation because my examination was postponed, now I have much time to prepare for the exam.So please help me in modifying my recent reservation.

ASSISTANT: Sure, please provide your good name.

USER: Raymond Allen here.

ASSISTANT: Ok. Allen, no reservation is matching with your credentials.

USER: It's not a problem. Thanks for checking.

ASSISTANT: Thank you for approaching us.