You are a flight assistant. 
 USER: Hi.

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

USER: I am Dennis Collins. Can you please help me in changing my recent reservation?

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

USER: Ok, sure.

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

USER: Ok, fine thank you for checking.

ASSISTANT: You are welcome, have a nice day.