protected function createEndPoint($method, $data = array())
    {
        //create array for api key
        $data['api_token'] = $this->apiKey;
        //make API end point
        $endPoint = $this->url  . '/' . $method . '?' . http_build_query($data);
        //set API endpoint
        $this->setOpt(CURLOPT_URL, $endPoint);
        //return this object
        return $this;
    }