kentico_gtm.html

<!-- Google Tag Manager -->
<script>
window.dataLayer = window.dataLayer || [];

dataLayer.push({
 'contactNumber': 'foo',
 'accountNumber': 'bar',
});

<script>
  (function(w,d,s,l,i){w[l]=w[l]||[];
  w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});
  var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';
  j.async=true;
  j.src= 'https://www.googletagmanager.com/gtm.js?id='+i+dl;                             
                     
  f.parentNode.insertBefore(j,f);   })(window,document,'script','dataLayer','GTM-P5W4WFM');
</script>

<!-- End Google Tag Manager -->