You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. Do you need any help from my side?

USER: I want to change my existing reservation, can you please help me in that?

ASSISTANT: Sure, I can help you and can I know your name for checking purpose?

USER: My name is Stephanie Carter.

ASSISTANT: Please allow me a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found for the user name in our data base to change your ticket booking.

USER: Ok, that's not a problem. Thanks for your information.

ASSISTANT: You are most welcome and thank you for reaching us.