Ajax.BeginForm loading result in page

I am trying to do an AJax form post, and when it is succesfull update a table with the results.

here is my code:

@using (Ajax.BeginForm("AddTagToSubject", "Subjects", null, new AjaxOptions() { OnSuccess = "UpdateTableData();" }, null))

{

    @Html.AntiForgeryToken()    

    <div class="form-">

        <div class="form-horizontal">

            @Html.Hidden("SubjectId", Model.Id)    

            <div class="form-group">

                @Html.Label("Add Tag", htmlAttributes: new { @class = "control-label col-md-2" })

                <div class="col-md-4">

                    @Html.TextBox("Tag", "", new { @class = "form-control" })

                </div>

                <div class="col-md-2">

                    <input type="submit" value="Add" class="btn btn-default" />

                </div>

            </div>

        </div>

    </div>

}

here is my script at bottom of page:

 <script type="text/javascript">

       //Get the latest tags

        function UpdateTableData() {

            console.log("Called fucntion");         

        }

   </script>

Here is my action method:

[HttpPost]

    public async Task<JsonResult> AddTagToSubject(AddTagToSubjectViewModel model)

    {

        model.Tag = model.Tag.ToLowerInvariant();

        var tags = await db.Tags.FirstOrDefaultAsync(x => x.Name == model.Tag);

        if (tags == null)

        {

            tags = new Tag { CreatedBy = User.Identity.GetUserId(), DateCreated = DateTime.UtcNow, Name = model.Tag };

            db.Tags.Add(tags);

            await db.SaveChangesAsync();

        }

        var subject = await db.Subjects.FirstOrDefaultAsync(x => x.Id == model.SubjectId);

        subject.Tags.Add(tags);

        await db.SaveChangesAsync();

        return Json(subject.Tags.Select(x => new { Id = x.Id, Name = x.Name }).ToList(), JsonRequestBehavior.AllowGet);

    }

Now when I add a tag, it calls the action method everything works. It adds the tag to the db. But on my front end, Instead of calling my JSON` result.

[{"Id":3,"Name":"Zulu"},{"Id":7,"Name":"accounting"},{"Id":6,"Name":"High School"}]

I have the following included in my layout file:

  bundles.Add(new ScriptBundle("~/bundles/jquery").Include(

                        "~/Scripts/jquery-{version}.js",

                        "~/Scripts/jquery.unobtrusive-ajax.js"

                        ));

What am I missing here?