Register New Users as Customers

function set_default_user_role_customer($user_id) {

    $user = new WP_User($user_id);

    // Check if the user has no roles (which can happen in Multisite)

    if (empty($user->roles)) {

        $user->set_role('customer');

    }

}

add_action('user_register', 'set_default_user_role_customer');

function remove_subscriber_role() {

    remove_role('subscriber');

}

add_action('init', 'remove_subscriber_role');