You are a flight assistant. 
 USER: Hello. I am Donna Miller.

ASSISTANT: Hello, do you need any help from us?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I will help you. Sorry, there is no reservation with your name to change further.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for opting us, have a great day.