You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

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

ASSISTANT: Sure, I will help you. Please wait a moment I will check the reservation list and I will inform you reservation is there or not.

USER: Ok, please make it as soon as possible.

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

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

ASSISTANT: Thank you.