404 Not Found calling Http Method from JavaScript in ASP

I've looked at a couple of threads now where they want to call a C# method from JavaScript in an ASP project. I can't figure out what I'm doing wrong. Here is my C# class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Services;

namespace Selfservice.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            return View();
        }

        [HttpGet]
        public String GetCredentials()
        {
            return User.Identity.Name.ToString();
        }
    }
}

And here is the JavaScript I'm trying to call:

window.onload = function () {
    LiveSearch();
    getCredentials();
    //FetchAllUsers();
};

function getCredentials() {
    $.ajax({
        type: 'POST',
        url: '@Url.Action("GetCredentials", "Home")',
        dataType: 'json',
        cache: false,
        contentType: 'application/json; charset=utf­8',
        data: JSON.stringify(""),
        success: function (cred) {
            alert(cred);
        },
        error: function (error) {
            alert(JSON.stringify(error));
        }
    });
}

I keep getting a 404 Not Found status back. It's an ASP site that's deployed on an IIS, on one of my workplaces servers. We are using Windows Authentication, so I'd like to get the credentials of whoever is logged in and store it for something else later.

I'm kind of at my wits end here. Anyone got any ideas?