public function sellUsingHostedData($hostedDataId, $amount, $comments = null, $invoiceNumber = null)
    {
        $service = $this->getService();

        $payment = new Model\Payment($hostedDataId, $amount);
        if (!empty($comments) || !empty($invoiceNumber)) {
            $transactionDetails = new Model\TransactionDetails('ns1', $comments, $invoiceNumber);
        } else {
            $transactionDetails = null;
        }
        $sellAction = new Request\Transaction\SellHostedData($service, $payment, $transactionDetails);

        return $sellAction->sell();
    }