You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I render you today?

USER: I am Donna Lewis. I want to change my existing reservation. Could you help with that?

ASSISTANT:  Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a while.

USER: Ok.

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

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.