Maybe the ban is stored at server side, but dont call him a noob because you dont know if he meant to remove the ban from the server, or just play when hes banned by evading the ban.
If you want to play when you are banned, there are few ways.
If you have static IP then use a proxy/VPN like HotspotShield or CyberGhostVPN
If you have dynamic IP, then just reboot your router or reset your connection in the router config page (i can refresh my ip in 5 seconds)
If you have dynamic IP, and you have been banned by range then try changing your ip, and if it still doesnt work use a proxy/VPN
If you have been banned on your nickname..then change it