You most likely are logged into the wrong account. You need to be logged into the main account, I.E. the one which can view the billing etc. To access the Web Safe page with any other account will leave you with an overview page and no control over Web Safe. Example image of being logged into the wrong account follows (complete with overview sample):
It would also be worthwhile using another web browser to access the page as it sounds like your current one isn't showing you the warning about being in the wrong account to administer the Web Safe settings.
- - - - - - Any opinions expressed by myself are entirely my own and do not represent Virgin Media in any way.