You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: Can you please help me to change my existing reservation?

ASSISTANT: Sure, I am here to help you. May I know your name to check with existing reservation?

USER: I am Patrick Roberts.

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

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for choosing us.