You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation due to business work, can you please help me?

ASSISTANT: Sure, I will help you to change your reservation. Can you please provide me your name?

USER: Thank you. Sure, I am Robert Lopez here.

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

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

ASSISTANT: Welcome, have a nice day.