protected function getApiInstance($method)
    {
        $gateway = Helper::className($this->getDriver());

        $class = "\\Shoperti\\PayMe\\Gateways\\{$gateway}\\".Helper::className($method);

        if (!class_exists($class)) {
            throw new BadMethodCallException("Undefined method [{$method}] called.");
        }

        return new $class($this->gateway);
    }