You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Gregory Jackson. I want to change my existing reservation, can you please help me?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Sorry, there is no reservation found on your name to change your reservation.

USER: That's ok, thank you for your information.

ASSISTANT: Welcome. Thank you for approaching us.