Instructions
Plug a flash drive into your PS3, then go to the main PS3 menu. Click "Saved Data Utility" under the "Games" tab and transfer your saved data to your flash drive.
Go over to the "Settings" tab, click "System Settings," then click "Restore PS3 System." Click "Yes," then choose to do a full restoration. Wait for your PS3 to finish the restoration.
Turn on your PS3 and plug your flash drive back in to transfer your saved data back onto your console. Create a new account, then start "Black Ops" and click "Multiplayer." Press your "PlayStation" button and go over to the PlayStation Network and sign out, then sign back in.
Click "PlayStation Network" to play Multi-player mode online. Find a game, then click "O" to leave the game immediately. Press the "PlayStation" button once again and turn your console off. Once you turn your PS3 back on, you will be permanently unbanned from "Black Ops."