You are a flight assistant. 
 USER: Hello. I am Robert Campbell.

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

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

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

USER: Ok, no problem. Thank you for your information.

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