Javascript to disable or enable radio buttons

I'm trying to do something a bit more complicated than this, but I broke it down and threw it in JSFIDDLE and I still can't get it to work.

Any suggestions?

JSFiddle

HTML:

<label for="service-type">Value</label>
<select id="service-type" onChange="hamburger()">
  <option>0</option>
  <option>1</option>
  <option>2</option>
  <option>3</option>
</select>
<label for="receiptNo">No</label>
<input type="radio" name="receipt" id="receiptNo">
<label for="receiptYes">Yes</label>
<input type="radio" name="receipt" id="receiptYes">

Javascript:

var e = document.getElementById("service-type");
var ServiceUser = e.options[e.selectedIndex].text;

function hamburger() {
   if (ServiceUser.value === "2") {
      document.getElementById("receiptNo").disabled = true;
      document.getElementById("receiptYes").checked = true; 
     } 
}