public function execute()
    {
        parent::execute();

        $xml = new DOMDocument();
        $hpsTransaction = $xml->createElement('hps:Transaction');
        $hpsCreditAddToBatch = $xml->createElement('hps:CreditAddToBatch');

        $hpsCreditAddToBatch->appendChild($xml->createElement('hps:GatewayTxnId', $this->transactionId));
        if ($this->amount != null) {
            $amount = sprintf("%0.2f", round($this->amount, 3));
            $hpsCreditAddToBatch->appendChild($xml->createElement('hps:Amt', $amount));
        }
        if ($this->gratuity != null) {
            $hpsCreditAddToBatch->appendChild($xml->createElement('hps:GratuityAmtInfo', $this->gratuity));
        }

        if ($this->directMarketData != null && $this->directMarketData->invoiceNumber != null) {
            $hpsCreditAddToBatch->appendChild($this->_hydrateDirectMarketData($this->directMarketData, $xml));
        }
        $hpsTransaction->appendChild($hpsCreditAddToBatch);
        $response = $this->service->doRequest($hpsTransaction);
        $this->_processChargeGatewayResponse($response, 'CreditAddToBatch');

        return $this->service
            ->get($this->transactionId)
            ->execute();
    }