protected function _wrapGatewayError($text)
{
    return Mage::helper('paygate')->__('Gateway error: %s', $text);
}

protected function _wrapGatewayError($text)
{
    if($text == 'This transaction has been declined.') {
        $text = 'Custom message here.';
    }
    return Mage::helper('paygate')->__('Gateway error: %s', $text);

}