You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you?

USER: Please help me to change my existing reservation as I need economy class ticket instead of business class. Can you please help me with this?

ASSISTANT: Sure, we are glad to help you.

USER: Thank you.

ASSISTANT: May I know your good name?

USER: Sure, I am Christopher Roberts.

ASSISTANT: We are sorry to inform you that, there is no active reservation on your name.

USER: Ok, Thank you for your help.

ASSISTANT: Thank you for opting us.