I've read many topics on this and nothing is working. I'm trying to do something really simple, but cant seem to get it to work. I'm trying to have the elements of a drop down box change the values in my paragraph text. Here is the script I'm running: 

```
<script>
    window.onload = function fn(){
    var x = document.getElementById("DescChange");
    var y = document.getElementById("CostChange");
    var a = document.getElementById("dropdown");

    a.addEventListener('change', function(){
        if (a.value == 0){
            x.innerHTML = "Description: Basic care for car including wax and buffer";
            y.innerHTML = "Total cost:" + 59.99;
        }
        else if (a.value == 1){
            x.innerHTML = "Mid-level care for car including Basic services and repainting";
            y.innerHTML = "Total cost:" + 119.99;
        }
        else if (a.value == 2){
            x.innerHTML = "Advanced care for car including Basic, Intermediate and interior + window repair";
            y.innerHTML = "Total cost:" + 299.99;
        }
        else{
            x.innerHTML = "";
            y.innerHTML = "";
        }

      });

    }
</script>

```

And here is my div with the select options: 

```
<div>
    <h2><u>Products and Services</u></h2>
    <h4>
        <select id="dropdown">
    <option value="empty"></option>
    <option value="0">Basic</option> 
    <option value="1">Intermediate</option> 
    <option value="2">Advanced</option> 
        </select>

    <p id="DescChange">1</p>
    <p id="CostChange">2</p>
    <p></p>
    <p></p>
    </h4>
</div>

```

I'm not getting any errors in my browser console. I feel like its something really easy that I'm missing, but I can't figure it out. I appreciate any help!

EDIT 1: I updated my script based off an answer below. Currently 1 `<p>` is updating: The advanced tag.... trying to find the discrepancies. 

Edit 2: its working. I messed up on if/else if statements.