Simple Implementation of MVC Cascading Ajax Drop Down is not working

Requirement :To display some-text in a Display-Box,when user changes values in a Dropdownlist.For this purpose i used PartialView, Ajax.BeginForm and Jquery.change function.

Issue : In the main-View* i am using **@html.Beginform() and @Ajax.BeginForm is used in partial view, so while i changes the value in Dropdownlist, Jquery Form submit is calling @html.Beginform() in main-View other than @Ajax.BeginForm

Expected Behavior:Jquery Form submit should call @Ajax.BeginForm in partial View

//following Scripts are included in View, Partial-View
<script src="~/Scripts/jquery-1.10.2.min.js"></script>
<script src="~/Scripts/jquery.validate.min.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.min.js"></script>


In Main View
@model Shopping.Models.Mob
//Issue:This "Html.BeginForm" is called during submitting from partial View
@using (Html.BeginForm("MobileSell", "MobileSell", FormMethod.Post))
{
<table>
<tr><td>**@Html.Partial("_SelectedMobileList", Model)**</td>
</tr>
<tr><td><div id="NextFields">**@Html.Partial("_SelectedMobileDetails", Model)**</div></td>
</tr>
</table>
}



In _SelectedMobileList Partial-View
@using (Ajax.BeginForm("FillMobileDetails", "MobileSell", new AjaxOptions { HttpMethod ="POST",
UpdateTargetId ="NextFields",
InsertionMode = InsertionMode.Replace}))
{
<td>@Html.DropDownListFor(x => x.MobileName, Model.MobileList, "select one", new { id="Drop1"})</td>
}

<script>
$(document).ready(fun1)

function fun1()
{ alert("test1"); $("#Drop1").change(fun2); }

function fun2()
{alert("test2");

//Jquery function calling submit-form
//Expected to invoke "Ajax.BeginForm" but invoking "html.BeginForm"
$(this).parents('form').submit();

}
</script>



In _SelectedMobileDetails Partial-View,which need to display test
@model Shopping.Models.Mob
@Html.DisplayFor(x=>x.MobileEmi)



In Controller
//Issue: Invoking this action-method.
public ActionResult MobileSell()
{
ObjectResult<sp_fetch_mobile_details_result> objResult = objContext.SP_Fetch_Mobile_Details();
SelectList objSelectList = new SelectList(objResult.ToList(), "MobileName", "MobileName");
objMobile.MobileList = objSelectList;
return View(objMobile);
}

[HttpPost]
//Excepted: To invoke this Action Method
public PartialViewResult FillMobileDetails(Mob Model)
{
Response.Write("test3");
Model=new Mob();
Model.MobileEmi="somEmi";
return PartialView("_SelectedMobileDetails",Model);
}

nb:Any doubts please may ask me and help me to fix this