You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: My name is Karen Miller. I want to change my existing reservation.

ASSISTANT: Sure, please wait a moment.

USER: OK.

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

USER: That's fine.

ASSISTANT: Thank you for reaching us, have a good day.

USER: Thank you for your help.