You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation. Could you help me with that?

ASSISTANT: May I know name please?

USER: Joshua Lopez here.

ASSISTANT: Sorry to say, there is no reservation on your name in our database.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.