How to call page method with a parameter through in a javascript event?

I have method like this in my .cs :

[System.Web.Services.WebMethod]
public static void GetServiceInformation(IInfo x) //IInfo  is an interface
{
    x.l_power = true;
    x.lb_InboxCount = UserTrans.GetInbox(int.Parse(emp_num), 0);
}

Now i want to call this method through a javascript method as a page method but it doesn't work .

<script type ="text/javascript">

    function GetInfo() {
        PageMethods.GetServiceInformation(this);
    }
   window.onload = setTimeout("GetInfo()", 3000);
</script>

  <telerik:RadScriptManager ID="RadScriptManager1" runat="server" EnablePageMethods="true">
  </telerik:RadScriptManager>

My .cs :

 public partial class AppMaster : Log, IInfo //My page
    {
        public string Inbox
        {
            get
            {
                return hpl_Inbox.NavigateUrl;
            }

            set
            {
                hpl_Inbox.NavigateUrl = value;
            }
        }
        public string Draft
        {
            get
            {
                return hpl_Draft.NavigateUrl;
            }

            set
            {
                hpl_Draft.NavigateUrl = value;
            }
        }

        public string New
        {
            get
            {
                return hpl_New.NavigateUrl;
            }
            set
            {
                hpl_New.NavigateUrl = value;
            }
        }
        public string Approved
        {
            get
            {
                return hpl_Approved.NavigateUrl;
            }
            set
            {
                hpl_Approved.NavigateUrl = value;
            }
        }
    //------- etc
 }

My interface :

public interface IInfo
    {
        string Inbox { get; set; }
        string Draft { get; set; }
        string New { get; set; }
        string Approved { get; set; }
        string archive { get; set; }
        string search { get; set; }
        string cand { get; set; }
        string pri { get; set; }
        string power { get; set; }
        string admin { get; set; }
        string help { get; set; }
        bool l_cand { get; set; }
        bool l_pri { get; set; }
        bool l_power { get; set; }
        bool l_admin { get; set; }

        string lb_ApprovedCount { get; set; }
        string lb_InboxCount { get; set; }
        string lb_archive { get; set; }
        string lb_DraftCount { get; set; }

    }