When I am on my Minecraft PC server a player has come on under my name and has had op and my rank. After I ban them they are able to change there names and come back I keep banning them and they keep coming back. Not really sure what to do.
You could try running your server with online mode (which means you might have to purchase a copy of Minecraft) so that players have to authenticate (proof that they're themself) themselves before they can join.
Otherwise a plugin like this (one that prevents play until you separately authenticate yourself after logging in) that prevents others from reusing a taken name also works.
Otherwise, what you'll have to live with it, and ban yourself (to stop others from using your name) and deop yourself whenever you log out.
To set your server to online mode, go to your
server.properties file and edit:
Either that or change your account's password and secure your email address.