You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, May I know what kind of service you are looking for?

USER: I want to change my existing reservation due to prepone of my exams. Can you help me in that?

ASSISTANT: Sure, I can change your reservation right now. Before that I need to know your good name please?

USER: Myself Larry Miller.

ASSISTANT: Thanks for providing your name, Please allow me a moment to check for the previous reservation in our database.

USER: Ok.

ASSISTANT: Thanks for remaining so positive, We are sorry to notify that there is no active reservation found on your name.

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

ASSISTANT: Thank you, For making us to serve you regarding change process.