You just have to delete "allowopenremotechat" "Allow user to open other users chats from same department" from operators role. Operator has to logout and login again.
Also, to operator has to be assigned explicity departments. If to operator is assigned all departments he still be able to open a chat. Also if user was the first who accepted he still be able to chat.
Developing application takes a lot of time. You can support application by donating. There is no company behind this application and it takes away my free time. Every donation matters and does not matter how small it is!