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

ASSISTANT: Hello, how may I help you today?

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

ASSISTANT: Sure, I am glad to help you. Please be on hold I will check and revert you.

USER: Sure.

ASSISTANT: There is no reservation found on your name in our database.

USER: No worries, thank you for the information.

ASSISTANT: Thank you for availing us.