You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you?

USER: I am Denis Moore. I would like to change my existing reservation, can you please help me in changing?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: Sorry, there is no active reservation found under your name in our records.

USER: Ok, not an issue. Thank you.

ASSISTANT: Most welcome.