How to change defaults posts types labels

Hi o/
I need to change to “Services” the labels of the post type “post”. I tried something like this:

add_action('init', 'init');
    function init(){
	    global $wp_post_types;
	    $wp_post_types['post']->labels->name = 'Services';
    }

But it not works. I think that is not the exact hook, I already tried: init, admin_init, after_setup_theme… but nothing happens. (I tried put outside of a hook too)
Someone knows something about it?
Thx =)