function plt_hide_pay_invoices_with_amazon_menus() {
//Hide the "Pay Invoices With Amazon" menu.
remove_menu_page('piwa');
//Hide the "Pay Invoices With Amazon → Settings" menu.
remove_submenu_page('piwa', 'piwa');
//Hide the "Pay Invoices With Amazon → Payments" menu.
remove_submenu_page('piwa', 'edit.php?post_type=amazon-payment');
}
add_action('admin_menu', 'plt_hide_pay_invoices_with_amazon_menus', 31);