You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, May I know your good name?

USER: I want to change my existing reservation which is with the name William Turner, as my office conference got postponed.

ASSISTANT: Ok, please wait  a moment I will check and revert you.

USER: Ok, sure.

ASSISTANT: Unfortunately there is no reservation found on your name.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Thank you for opting us.