protected function detectMnc($lc, $carrierName)
  {
      $fp = fopen(__DIR__.DIRECTORY_SEPARATOR.'networkinfo.csv', 'r');
      $mnc = null;

      while ($data = fgetcsv($fp, 0, ',')) {
          if ($data[4] === $lc && $data[7] === $carrierName) {
              $mnc = $data[2];
              break;
          }
      }

      if ($mnc == null) {
          $mnc = '000';
      }

      fclose($fp);

      return $mnc;
  }