public function getWsdlUrl()
    {
        // overriding wsdl url
        if (($sWsdl = \OxidEsales\Eshop\Core\Registry::getConfig()->getConfigParam("sVatIdCheckInterfaceWsdl"))) {
            $this->_sWsdl = $sWsdl;
        }

        return $this->_sWsdl;
    }