You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you ?

USER: I want to change my existing reservation, can you please help me in this?

ASSISTANT: Sure, may I know your name?

USER: Brandon Carter is my name.

ASSISTANT: Please stand by, I will revert to you.

USER: Ok, sure.

ASSISTANT: Unfortunately, there is no reservation found with your name in our database.

USER: Ok, that's not an issue. Thanks for the information.

ASSISTANT: Thanks for approaching us.