You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

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

ASSISTANT: Sure, may I know your name please?

USER: I am Dennis Carter.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

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

ASSISTANT: Thank you for opting us.