there is many way, but for this you need to add a function in webservice.

<script type="text/javascript" src="script/jquery-1.3.2.min.js"></script>
  <script type="text/javascript">
    $(document).ready(function() {
      $('#Customers').change(function() {
        $.ajax({
          type: "POST",
          contentType: "application/json; charset=utf-8",
          url: "FetchCustomer.asmx/GetCustomer",
          data: "{ CustomerID: '" + $('#Customers').val() + "'}",
          dataType: "json",
          success: function(data) {
            $("#CustomerDetails").html(data.d);
          }
        });
      });
    });
</script>

http://forums.asp.net/p/1564134/3889173.aspx#3889173

http://francstratton.com/jQueryAJAXCall.aspx



happy coding