You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Donna Nelson. I am planning to change an existing reservation, due to some urgent work. Can you please change my reservation?

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name to change your reservation?

USER: That's fine. Thank you for your service.

ASSISTANT: Thank you for reaching us.