HttpPost doesn't work into Modal Popup in MVC 4 - asp.net-mvc-4

Question

I have view that has CompanyTable partial view. So this partial view has a CreateBankAccount partial view. Last partial view codes are
#model Invoice.Model.BankAccount
<script src="~/Scripts/jquery-1.7.1.min.js"></script>
<script src="~/Scripts/jquery.validate.min.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.min.js"></script>
Launch demo modal
<div id="#Model.TaxID" class="modal hide fade" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
<h3 id="myModalLabel">Modal header</h3>
</div>
<div class="modal-body">
#using (Ajax.BeginForm("CreateModal", "CompanyController", new AjaxOptions { UpdateTargetId = "modal", HttpMethod = "post" }))
{
#Html.ValidationSummary(true)
<fieldset>
<legend>BankAccount</legend>
#Html.HiddenFor(model => model.ID)
<div class="editor-label">
#Html.LabelFor(model => model.BankName)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.BankName)
#Html.ValidationMessageFor(model => model.BankName)
</div>
<div class="editor-label">
#Html.LabelFor(model => model.CorrespondentAccount)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.CorrespondentAccount)
#Html.ValidationMessageFor(model => model.CorrespondentAccount)
</div>
<input type="submit" value="save" />
</fieldset>
}
</div>
<div class="modal-footer">
<button class="btn" data-dismiss="modal" aria-hidden="true">Close</button>
<input type="submit" class="btn btn-primary" value=" Save changes" data-dismiss="modal" />
</div>
</div>
so this partial view is modal popup. My problem is that when I want to creat bankAccount my HttpPost method doesn't work, and I return Index action. How I can fix it?