How to update view model in a partial view in MVC5?

I have a View and inside that view I have a div that will contain a partial view.

My issue is this. The user selects an item from the dropdownlist and I load the partial view with the model. The user change changes some of the textboxes and clicks the button to submit the partial view (which is in a Html.BeginForm).

When I go to examine the model in the controller the model doesn't contain the changes that the user made.

Why doesn't the model reflect the changes the user made?

In the main view:

<div id="personInfo" style="display:none;"></div>

My partial view:

    @model MyProject.MyModel

    @(Html.Kendo().DropDownList().Name("ddlFilters")
                                .AutoBind(true)
                                .OptionLabel("--- Select Filter ---")
                                .DataValueField("ID")
                                .DataTextField("MYFILTER")
                                .DataSource(ds =>
                                    ds.Read(r => r.Action("GetPersonFilters", "Home"))
                                )
                                .Events(x => x.Select("ddlFilters_onSelect"))
                        )

    @using (Html.BeginForm("PersonAction", "Home", FormMethod.Post, new { @class = "form-horizontal", id = "personForm" }))
            {
                 // Strongly typed Kendo fields. Several DropDownListFor and TextBoxFor
                 @Html.Kendo().TextBoxFor(x => x.FirstName).HtmlAttributes(new { @class = "form-control kendoTextBox required " })
                // Button to post the form data to the controller.
            }

My Javascript:

function ddlFilters_onSelect(e) {
    var itm = this.dataItem(e.item);

    clearForm();

    if (itm.ID > 0) {
        // Ajax call to get data....
        $.ajax({
            url: "/Home/GetPerson",
            type: "GET",
            data: { "myID": itm.ID }
        })
        .done(function (result) {
            //var aaa = data;      
            $("#personInfo").html(result);
        })
        .fail(function (xhr, status, err) {
            alert(xhr.responseText);
        });
    }
};

Model:

 public partial class MyModel
    {
        public decimal ID { get; set; }
        public string FirstName{ get; set; }
        public string LastName{ get; set; }
        public string MiddleName{ get; set; }
    }

EDIT: Controller Code:

 // Initial call to main view
    public ActionResult CreateNewPerson()
    {
        return View();
    }

    // Call to load Partial View initially
    public PartialViewResult GetPersonInfo()
    {
        return PartialView("_PersonForm", new MyModel());
    }

    // Call to load partial view with data
    public PartialViewResult GetPerson(int myID)
    {
        myData = GetFromDB(myID);
        return PartialView("_PersonForm", myData);
    }

    // Method to save partial form
    [HttpPost]
    public ActionResult PersonAction(MyModel filter)
    {           

        if (ModelState.IsValid)
        {
            // Go update DB
        }

        return View("CreateNewPerson");
    }