code: public function getCellByColumnAndRow($columnIndex, $row, $createIfNotExists = true)
      {
          $columnLetter = Coordinate::stringFromColumnIndex($columnIndex);
          $coordinate = $columnLetter . $row;
  
          if ($this->cellCollection->has($coordinate)) {
              return $this->cellCollection->get($coordinate);
          }
  
          // Create new cell object, if required
          return $createIfNotExists ? $this->createNewCell($coordinate) : null;
      }
docs: Get cell at a specific coordinate by using numeric cell coordinates.
  
  @param int $columnIndex Numeric column coordinate of the cell
  @param int $row Numeric row coordinate of the cell
  @param bool $createIfNotExists Flag indicating whether a new cell should be created if it doesn't
  already exist, or a null should be returned instead
  
  @return null|Cell Cell that was found/created or null