As pointed out, you can't ban from IP as most have dynamic IP address's and rebooting the router sometimes changes it, not always instantly. There are other means for blocking an IP address from a certain provider, but blocking the transport could also block anyone else who is with that provider. You can however, contact the users ISP and find out what range of IP's are being used in their area and block the whole lot. You will have to be a bit clever when doing this, as they won't just give you the IP range by normal request.
/Phantom