You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donna Hall.

ASSISTANT: How can I help you out?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure. Can you please wait for a minute?  I will check the reservation list and revert to you.

USER: Sure.

ASSISTANT: Thanks for your time. I have gone through the reservation list recorded in our database, but we did not find your name.

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

ASSISTANT: Thank you for choosing us, Have a great day.