public function toArray()
    {
        $messages = [];
        $receivers = [];

        /** @var ShortMessage $shortMessage */
        foreach ($this->items as $shortMessage) {
            $messages[] = $shortMessage->body();
            $receivers[] = $shortMessage->receiversString();
        }

        return [
            'Msisdns'        => implode('|', $receivers),
            'Messages'       => implode('|', $messages),
        ];
    }