You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: I am Andrew Brown.

ASSISTANT: Ok.

USER: Please change my existing reservation due to my health issue.

ASSISTANT: Sure, Please wait a while.

USER: Sure.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your ticket, but could not find any reservation with your name.

USER: Ok, Not an issue. Thank you.

ASSISTANT: Thank you for reaching us.