public static function containsUCS2Characters($string)
    {
        $GSMCharsetAsString = implode(array_keys(GSMCharset::$GSMCharset));

        foreach (self::mb_str_split($string) as $char) {
            if (mb_strpos($GSMCharsetAsString, $char) === false) {
                return true;
            }
        }

        return false;
    }