public string AddCallBack(CallBack callBack)
 {
     try
     {
         Guid     g         = Guid.NewGuid();
         DateTime now_date  = DateTime.Now;
         CallBack callBack1 = new CallBack {
             Id = g, Name = callBack.Name, PhoneNumber = callBack.PhoneNumber, DateNow = now_date
         };
         _repo.AddCallBack(callBack1);
         return("true");
     }
     catch (Exception e)
     {
         return(e.ToString());
     }
 }