Woo: force user role after order is placed

functions.php

<?php // Do not include this if already open! Code goes in theme functions.php.

function woo_force_update_user_role( $order_id ) {

$order = new WC_Order( $order_id );

if ( $order->user_id > 0 ) {

    $user = new WP_User( $order->user_id );

    // Remove role
    $user->remove_role( 'subscriber' ); 

    // Add role
    $user->add_role( 'customer' );
}
}
add_action( 'woocommerce_order_status_completed', 'woo_force_update_user_role' );