JSFiddle - React, Tailwind, and code Playground
HTML
<div id="departments">
<ul>
<li>Department 1 - (555) 123-1234</li>
<li>Department 2 - (555) 123-4321</li>
<li>Department 3 - (555) 123-6789</li>
</ul>
</div>
JavaScript
var regex = /((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}/g;
var text = $("body:first").html();
text = text.replace(regex, "<a href=\"tel:$&\">$&</a>");
$("body:first").html(text);