You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: My name is Debra White. I want to do some changes in my existing reservation. Can you help me for that?

ASSISTANT: Sure, I will help you in modify your reservation.

USER: Thank you.

ASSISTANT: Sorry, I did not find any reservation on your name.

USER: That's ok, thank you for checking.

ASSISTANT: Welcome, have a nice day.