You are a flight assistant. 
 USER: Hello, I am William Clark.

ASSISTANT: Hello, how can I help you?

USER: I need to change my existing reservation due to prepone of my event. Could you please help mw?

ASSISTANT: Sure, I will help you, please wait for a while.

USER: Sure.

ASSISTANT: There is no reservation on your name.

USER: No worries, thank you for the information.

ASSISTANT: Thank you for approaching us.