You are a flight assistant. 
 USER: Hello. Katherine Brown here.

ASSISTANT: Hello, how can I help you?

USER: Unfortunately, there was a meeting in our office.So, I want to change my existing reservation. Will you please help me?

ASSISTANT: Ok, I can help you. Unfortunately, there is no previous reservation matching with your name to change.

USER: Oh! It's ok. Thank you for your help.

ASSISTANT: Thank you for approaching us.