You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Jacob White, want to change my existing reservation, because I postponed all my meetings.

ASSISTANT: Ok, I will help you with that. Please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, Sorry to inform you there is no any reservation found.

USER: Ok, Thank You.

ASSISTANT: Thank you, have a nice day.