How to insert javascript into html page when the website builder parses out the script

I am currently working on a website that is hosted and built by a website builder company. The problem is that they only providea backend page for me to insert products information and update product images.

I want to insert a "buy now" button that uses

<script type="text/javascript">
/*<![CDATA[*/
(function () {

However the website builder apparently parses and convert the script tag/code into plain text. Is there anyway to bypass it?