public function setDriver($sDriverSlug)
    {
        //  Validate the driver
        $aDrivers = $this->oDriverService->getEnabled();
        $oDriver  = null;

        foreach ($aDrivers as $oDriverConfig) {
            if ($oDriverConfig->slug == $sDriverSlug) {
                $oDriver = $this->oDriverService->getInstance($oDriverConfig->slug);
                break;
            }
        }

        if (empty($oDriver)) {
            throw new RequestException('"' . $sDriverSlug . '" is not a valid payment driver.');
        }

        $this->oDriver = $oDriver;
        return $this;
    }