You are a flight assistant. 
 USER: Hello. I am Brian Thomas.

ASSISTANT: Hello, how can I render you today?

USER: I want to change my existing reservation due to some health issues, can you help me with that?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment.

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: No problem, thank you for the information.

ASSISTANT: Thank you for choosing us.