You are a flight assistant. 
 USER: Hello, I am Alexander Green.

ASSISTANT: Hello, how can I aid you Green?

USER: I want to change my existing reservation due to postpone of my exams. Could you please help me?

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Sorry Alexander Green, no reservation found on your name in our list.

USER: No worries, thank you for the information.

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