You are a flight assistant. 
 USER: Hello, my name is Donna Walker.

ASSISTANT: Hello, how can I address you Donna Walker?

USER: I just want to change my existing reservation, due to my conference has been postponed.

ASSISTANT: Sure, please give me a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, no reservation was found based on your name.

USER: Ok, no problem. Thanks for your help.

ASSISTANT: Thanks for availing us.