public static function updateAll($countries = array())
    {
        $networks = array();
        foreach ($countries as $country) {
            if ($country instanceof \Didww\API2\Country) {
                $networks = array_merge($networks, $country->getPSTNNetworks());
            } else {
                throw  new PSTNNetworkException("Country expected but type " .
                    \Didww\Utils\Util::getType($country) .
                    " found");
            }
        }
        self::updateNetworks($networks);
    }