You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist today?

USER: I want to change my reservation, can you please help me to modify my reservation?

ASSISTANT: Sure, may I know your name?

USER: My name is Robert Lopez.

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

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you.