You can instruct Knockout to explicitly 'escape' the View-Model scope by using the window
keyword:
<div class="col-lg-6" data-bind="visible: window.UserData.IsPayingUser">
And in your JavaScript:
window.UserData = { IsPayingUser = ko.observable(false) };
It's worth noting though that the 'Knockout way' to do it is to use nested View-Models and try to avoid pollution of the global scope.