Why My Webservice Throw Exception When I Execute My Stored Procedure ?

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C#

SQL

service

web

DECLARE @WarrantyCode AS NVARCHAR(20)
DECLARE	@Serial AS NVARCHAR(50) 
DECLARE	@ProductTitle AS NVARCHAR(50) 
DECLARE	@ShopCenter AS NVARCHAR(70) 
DECLARE	@AddDate DATE 
DECLARE	@Bill AS NVARCHAR(50) 



SET @WarrantyCode = '123456rrrrrrrr'
SET	@Serial = '123456rrrxxx'
SET	@ProductTitle= '123456' 
SET	@ShopCenter= '123456'
SET	@AddDate = '2014-01-01'
SET	@Bill = '123456' 

DECLARE @url as nvarchar(256)
Declare @Obj as Int;
Declare @Response as Varchar(8000);
DECLARE @hr AS INT
DECLARE @src AS VARCHAR(MAX)
DECLARE @desc AS VARCHAR(MAX)


 SET @url = 'http://MY IP:9671/MyWebService.asmx/Upload?WarrantyCode=' + @WarrantyCode + '&Serial=' + @Serial + '&ProductTitle=' + @ProductTitle + '&ShopCenter=' + @ShopCenter + '&AddDate=' + CAST(@AddDate AS NVARCHAR(20)) + '&Bill=' + @Bill
	Exec @hr=sp_OACreate 'MSXML2.XMLHTTP', @Obj OUT
	EXEC sp_OACreate 'MSXML2.ServerXMLHttp.3.0', @obj OUT
    EXEC sp_OAMethod @obj, 'open', NULL, 'POST', @url, false
    EXEC sp_OAMethod @obj, 'send'
    EXEC sp_OAGetProperty @obj, 'ResponseText', @Response OUTPUT 
    SELECT @url AS URL, @Response AS [response], CHARINDEX('amiressami.com', @Response) AS IsOK, CHARINDEX('Hello', @Response) AS Result
    EXEC sp_OADestroy @obj

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
using System.Web.Services;

/// <summary>
/// Summary description for MyWebService
/// </summary>
[WebService(Namespace = "http://amiressami.com/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// 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 MyWebService : System.Web.Services.WebService
{
    [WebMethod]
    public string Upload(string WarrantyCode, string Serial, string ProductTitle, string ShopCenter, string AddDate, string Bill)
    {
        SqlCommand cmd = new SqlCommand();
        cmd.Connection = new SqlConnection(Roozbeh.CnnStr);
        cmd.CommandText = "INSERT INTO Guarranty VALUES (@WarrantyCode, @Serial, @ProductTitle, @ShopCenter, @AddDate, 1, @Bill)";
        cmd.Parameters.AddWithValue("@WarrantyCode", WarrantyCode);
        cmd.Parameters.AddWithValue("@Serial", Serial);
        cmd.Parameters.AddWithValue("@ProductTitle", ProductTitle);
        cmd.Parameters.AddWithValue("@ShopCenter", ShopCenter);
        cmd.Parameters.AddWithValue("@AddDate", AddDate);
        cmd.Parameters.AddWithValue("@Bill", Bill);
        try
        {
            cmd.Connection.Open();
            cmd.ExecuteNonQuery();
            return "Roozbeh"; //OK
        }
        catch (Exception ex)
        {
            return ex.Message;
        }
        finally
        {
            cmd.Connection.Close();
        }
    }

}

When I execute my SQL Server QUERY I got the posted url and XML result posted by my web service in my query analyzer
so I have the generated url by my query same as:

http://MY IP:9671/MyWebService.asmx/Upload?WarrantyCode=123456rrrrrrrr&Serial=123456rrrxxx&ProductTitle=123456&ShopCenter=123456&AddDate=2014-01-01&Bill=123456


and my result always is:

System.InvalidOperationException: Request format is invalid: .
at System.Web.Services.Protocols.HttpServerProtocol.ReadParameters()
at System.Web.Services.Protocols.WebServiceHandler.CoreProcessRequest()



but when I copy the generated query to my browser its work without any problem