You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

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, can I know your name please?

USER: Steven Miller here.

ASSISTANT: Sorry Steven, there is no reservation found with your name in our records.

USER: It's ok. Thanks for your checking.

ASSISTANT: It's our pleasure.