You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: I want to change my existing reservation due to sudden postpone of my trip dates. Can you help me out?

ASSISTANT: Sure, I'm always here to help you. Can I have your good name please?

USER: Thank you. I am Donald Anderson.

ASSISTANT: Ok, please give me a minute to check your reservation status.

USER: Sure.

ASSISTANT: Donald Anderson, there is no active reservation found under your name in our database to do modifications in that.

USER: Ok, no problem. Thank you.

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