You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, May I know your name?

USER: I am Dennis Evans.

ASSISTANT: Please wait a second.

USER: Sure.

ASSISTANT: Sorry, No reservation found on your name.

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

ASSISTANT: Thank you for opting us.