asp.net ช่วยด้วยครับ ajax call webservice ไม่ได้ครับ ไม่รู้ทำงัยดี

namespace SrifaGroup.Ui.Web.Services
{
    /// <summary>
    /// Summary description for FontCencalBill
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
    [System.Web.Script.Services.ScriptService]
    public class FontCencalBill : System.Web.Services.WebService
    {
        public FontCencalBill()
        {
        }

        [WebMethod]
        public string Save(string datetime, string DateDoc, string NumDoc, string disply, string user, string department, string remark)
        {
             
            string ddat, b;
            string data = "AAAA";
            ddat = datetime;
            b = DateDoc;

            return data;
        }
    }
}