Hi Javierabdo,
To unlink any account from (PSN, XBOX, or FACEBOOK) you must contact Support. Once this is done you will be able to link any account again by signing into Uplay from the game, while logged into PSN, XBL or Facebook.
Here is a link for account unlinking, which will direct you to Support:
http://ubisoft-en.custhelp.com/app/a...SEY0akZZZmw%3D
Please create a ticket to support by clicking on the “Ask a Question” tab on the top of the page at http://support.ubi.com/
When ready: >> HOW TO LINK YOUR PSN ACCOUNT
As soon as you register a Uplay account within a uplay-enabled game on your console, or log in with an existing account, it becomes linked with your PSN ID or XBL acccount
- login to PSN / XBL
- launch Uplay from the main menu
- log in with your account credentials
More recent games have an integrated form which will prompt for registration, but at least the steps above work for all games.