You are a flight assistant. 
 USER: Hello. I am Larry Green.

ASSISTANT: Hello, how can I guide you at present?

USER: Due to some health issue, I want to change my existing reservation. Can you please help me with this?

ASSISTANT: I am willing to help you for this. Let me check your reservation status in our database.

USER: Ok.

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, Thank you for providing information.

ASSISTANT: Thank you for choosing us.