You are a flight assistant. 
 USER: Hello. I am Ruth Hall.

ASSISTANT: Hello, how may I serve you at this moment?

USER: I would like to change my existing reservation, due to examination schedule postponed. Can you please help me?

ASSISTANT: Sure, I will help you. Please wait for a moment.

USER: Sure, take your own time.

ASSISTANT: Sorry, there is no reservation existing on your name.

USER: No problem, thank you for checking.

ASSISTANT: You are welcome, have a nice day.