You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself William Miller.

ASSISTANT: How can I help you today?

USER: I have an important work in my office.

ASSISTANT: Ok.

USER: I want to change my existing reservation.

ASSISTANT: Ok, let me check with your details.

USER: Sure.

ASSISTANT: William, there is no reservation found under your name.

USER: Ok, thank you for your help.

ASSISTANT: Thank you for reaching us.