phpspreadsheet read and getting values using header (1st row value)

<?php
use Phppot\DataSource;
use PhpOffice\PhpSpreadsheet\Reader\Xlsx;

require_once 'DataSource.php';
$db = new DataSource();
$conn = $db->getConnection();
require_once ('./vendor/autoload.php');

        $allowedFileType = [
            'application/vnd.ms-excel',
            'text/xls',
            'text/xlsx',
            'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
        ];

        $targetPath = 'uploads/test.xlsx';
        $Reader = new \PhpOffice\PhpSpreadsheet\Reader\Xlsx();

        $header = ["Tracking_Number", "Referance"];

        $spreadSheet = $Reader->load($targetPath);
        $excelSheet = $spreadSheet->getActiveSheet();
        $spreadSheetAry = $excelSheet->toArray();
        $sheetCount = count($spreadSheetAry);
        
        for ($i = 0; $i <= $sheetCount; $i ++) {
            $TN = "";
            if (isset($spreadSheetAry[$i][0])) {
                $TN = mysqli_real_escape_string($conn, $spreadSheetAry[$i][0]);
            }
            
            $RF = "";
            if (isset($spreadSheetAry[$i][1])) {
                $RF = mysqli_real_escape_string($conn, $spreadSheetAry[$i][1]);
            }

            echo $TN." - ".$RF."<br/>";
        }
?>