WebService response is null

Below is the entire code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
//using PriceAPI.ProgressPriceAPI;
using System.Globalization;
using System.Xml;
using System.Xml.Serialization;
using System.IO;
using System.Text;
using PriceAPI.ProgressPriceAPI ;
namespace PriceAPI
{
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

}

protected void Button1_Click(object sender, EventArgs e)
{
try
{

CultureInfo clf = new CultureInfo("en-US");

GetRenewalPriceReqType[] pricereqtype = new GetRenewalPriceReqType[1];
ProgressPriceAPI.SSIGetRenewalPriceListSrvService PricingRequestObj = new SSIGetRenewalPriceListSrvService();
ProgressPriceAPI.GetRenewalPriceResType[] PricingResponseObj ;
ProgressPriceAPI.GetRenewalTaxType[] txprice;
//txprice = new GetRenewalTaxType[1];
pricereqtype[0] = new GetRenewalPriceReqType();
pricereqtype[0].Domain = "USA";
pricereqtype[0].ContractNumber = "153452";
pricereqtype[0].ContractLine = 5;
pricereqtype[0].AdjustPriceRenewal = "A";
pricereqtype[0].ServiceLevel = "STDNEW";
pricereqtype[0].TaxBasisAmount = 0;

pricereqtype[0].ContractLineSpecified = true;
pricereqtype[0].EffectiveDateSpecified = true;
pricereqtype[0].TaxBasisAmountSpecified = true;
string strDate = "2011-11-30";
DateTimeFormatInfo dtfi = new DateTimeFormatInfo();
dtfi.ShortDatePattern = "YYYY-MM-DD";
dtfi.DateSeparator = "-";
DateTime objDate = Convert.ToDateTime(strDate, dtfi);

pricereqtype[0].EffectiveDate = objDate;
ObjectToXml(pricereqtype[0], "c:\\pricereqtype.xml");
//PricingResponseObj = new GetRenewalPriceResType[2];

PricingResponseObj = PricingRequestObj.SSIGetRenewalPriceListSrv(pricereqtype);
Label1.Text = "Success";


}
catch (Exception ex) {
Label1.Text = ex.Message;
}

}

private void GetPrice()
{
//ProgressPriceAPI.
}

public static void ObjectToXml(object obj, string path_to_xml)
{
//serialize and persist it to it's file
try
{

System.Xml.Serialization.XmlSerializer writer =
new System.Xml.Serialization.XmlSerializer(obj.GetType());
System.IO.StreamWriter file =
new System.IO.StreamWriter(path_to_xml);

writer.Serialize(file, obj);
file.Close();
//XmlSerializer ser = new XmlSerializer(obj.GetType());
//FileStream fs = File.Open(
// path_to_xml,
// FileMode.OpenOrCreate,
// FileAccess.Write,
// FileShare.ReadWrite);
//ser.Serialize(fs, obj);
}
catch (Exception ex)
{
throw new Exception(
"Could Not Serialize object to " + path_to_xml,
ex);
}
}
}
}