You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I support you?

USER: I am Brain Lee. I need to change my existing reservation, Can you please help with that?

ASSISTANT: Sure, let me check the data base and revert you.

USER: Sure.

ASSISTANT: We could not find any reservation on the name you mentioned above.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for opting us.