JQuery bind/unbind mousewheel event

I am trying to enable and disable scrolling on my page

I have this function :

function scroll_toggle(key){
    if (key) {
        $(window).bind('scroll', function(){
            $('body').on({
                'mousewheel': function(e) {
                    console.log("binded");
                    $("html body").scrollTop(0);
                    if (e.target.id == 'el') return;
                    e.preventDefault();
                    e.stopPropagation();
                }});
        });
    } else {
        $(window).unbind('scroll');
         $('body').on({
                'mousewheel': function(e) {
                    console.log("unbinded");
                    return true;

                }});
    }
}

When I call this function for the first time with true as parameter, the mousewheel don't work, and a I have "binded" in my console.

But when I call the function with false, the mousewheel still don't work and i have "binded" and "unbinded" alternatively.

What is wrong in my code?

Thanks for your time