Change the Labels of Users to Customers in Admin

Ok, I've been searching for over an hour for something I thought (and still think) is pretty simple. I need to change the title Users to Customers in the admin for a client. I can and have easily hooked into the menus and changed it there. But it still shows up as Users on the main users page or when you add a new user (Add new User should be Add New Customer).

I tried something like this in an init action but no dice ...

$labels = &$wp_post_types['users']->labels; $labels->name = 'Customer'; 

I've got to be missing some very simple filter. Thanks for your help!