It's very simple to remove a user from your VIPs list once you have added them. You simply need to click on the Free section in the Contact section in your Settings tabs. By doing so, you will remove that user from your free selection.
You can also remove a user that was previously on your free list by going to their profile and clicking on the highlighted "Free" button. This will remove this particular user from your list (make sure this user was previously a Free of yours; if not you might be adding this user to your free list).
You can check your free list at anytime in the Free tabs in your Contact in your Settings.