so sollte es aussehen

Api.php

<?php
/**
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/osl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@magentocommerce.com so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade Magento to newer
 * versions in the future. If you wish to customize Magento for your
 * needs please refer to http://www.magentocommerce.com for more information.
 *
 * @category    Mage
 * @package     Mage_Customer
 * @copyright   Copyright (c) 2012 Magento Inc. (http://www.magentocommerce.com)
 * @license     http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */

/**
 * Customer api
 *
 * @category   Mage
 * @package    Mage_Customer
 * @author     Magento Core Team <core@magentocommerce.com>
 */
class Interwall_EvolverSSOIntegration_Model_Customer_Api_V2  extends Mage_Customer_Model_Customer_Api_V2
{

    private $_attributeCode = array(
        'debit_payment_acount_blz',
        'debit_payment_acount_number'
        );
    /**
     * Retrieve customers data
     *
     * @param  object|array $filters
     * @return array
     */
    public function items($filters)
    {
        $collection = Mage::getModel('customer/customer')->getCollection()->addAttributeToSelect('*');
        /** @var $apiHelper Mage_Api_Helper_Data */
        $apiHelper = Mage::helper('api');
        $filters = $apiHelper->parseFilters($filters, $this->_mapAttributes);
        try {
            foreach ($filters as $field => $value) {
                $collection->addFieldToFilter($field, $value);
            }
        } catch (Mage_Core_Exception $e) {
            $this->_fault('filters_invalid', $e->getMessage());
        }
        $result = array();
        foreach ($collection as $customer) {
            $data = $customer->toArray();
            $row  = array();
            foreach ($this->_mapAttributes as $attributeAlias => $attributeCode) {
                $row[$attributeAlias] = (isset($data[$attributeCode]) ? $data[$attributeCode] : null);
            }
            foreach ($this->getAllowedAttributes($customer) as $attributeCode => $attribute) {
                if (isset($data[$attributeCode])) {
                    $row[$attributeCode] = $data[$attributeCode];
                }
            }
            foreach($this->_attributeCode as $_code){
                if(in_array($_code, $row)){
                    $tmp = $row[$_code];
                    $row[$_code] = MAge::helper('core')->decrypt($tmp);
                }
            }
            $result[] = $row;
        }

        return $result;
    }
} // Class Mage_Customer_Model_Customer_Api End