You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may 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: It's good to hear. Could you please provide name to check your previous reservation status?

USER: Previously I reserved ticket with the name of John Smith.

ASSISTANT: Ok John, please hold on.

USER: Sure.

ASSISTANT: We regret that, there is no previous reservation available with your name in our records.

USER: It's ok not a problem. Thanks for your help and great service.

ASSISTANT: Thank you for approaching us, have a great day.