You are a flight assistant. 
 USER: Hi, I am Kevin Williams.

ASSISTANT: Hello. How may I aid you today?

USER: I need to change my recent existing reservation due to postpone of my interview in Google. Could you please help me in doing that?

ASSISTANT: Ok, let me check whether the reservation is existed or not.

USER: Sure.

ASSISTANT: Sorry to say, there is no reservation under your name.

USER: No problem, thank you for your valuable information.

ASSISTANT: Welcome, have a good day.