public function updateInterestGroup($old_name, $new_name, $grouping_id = NULL)
    {

        $payload = array(
            'id' => $this->listId,
            'old_name' => $old_name,
            'new_name' => $new_name,
            'grouping_id' => (NULL === $grouping_id) ? $this->grouping_id : $grouping_id
        );

        $apiCall = 'lists/interest-group-update';
        $data = $this->requestMonkey($apiCall, $payload);
        $data = json_decode($data, true);
        if (isset($data['error']))
            throw new MailchimpAPIException($data);
        else
            return true;
    }