GET http://localhost:xxxxx/service1.svc/data? Columnname=colname 400 (bad request)

$(document).ready(function () {
    $('.filter').click(function () {

        var pos = $(this).position();
        var width = $(this).outerWidth();
        var height = $(this).outerHeight();
        var colName = $(this).attr("alt");

        jQuery.support.cors = true;

        $.ajax({

            type: "GET",
            url: "http://localhost:61832/Service1.svc/data?ColumnName=" + colName,
            processData: false,
            contentType: "application/json; charset=utf-8",
            dataType: "json",

            success: function (response) {

              // doing something

            },
            error: function (xhr, status, error) {
                alert(error);
            }
        });

    });
    $(document).mouseup(function (e) {
        var container = $("#divFilterList");

        if (container.has(e.target).length === 0) {
            container.detach();
        }
    });
});

<system.serviceModel>
    <behaviors>
      <serviceBehaviors>
        <behavior>
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="false"/>
        </behavior>
      </serviceBehaviors>
      <endpointBehaviors>
        <behavior name="WebBehavior">
          <webHttp />
        </behavior>
      </endpointBehaviors>
    </behaviors>
    <bindings>
      <wsHttpBinding>
        <binding name="NoSecurity">
          <security mode="None"/>
        </binding>
      </wsHttpBinding>
    </bindings>
    <services>
      <service name="GRDIVIEW EXCEL FILTER.Service1">
        <endpoint address="" behaviorConfiguration="WebBehavior" binding="webHttpBinding" contract="GRDIVIEW EXCEL FILTER.IService1"/>
      </service>
    </services>
    <serviceHostingEnvironment multipleSiteBindingsEnabled="true" />
  </system.serviceModel>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
using System.ServiceModel.Web;

namespace GRIDVIEW_EXCEL_FILTER
{
    [ServiceContract]
    public interface IService1
    {
        [OperationContract]
        [WebGet(UriTemplate = "/data?ColumnName={strColumnName}", ResponseFormat = WebMessageFormat.Json)]
        FilterValueSet[] GetDistinctValue(string strColumnName);
    }
}

using System;
using System.Collections.Generic;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Activation;
using System.ServiceModel.Web;
using System.Text;
using Oracle.DataAccess.Client;
using Oracle.DataAccess.Types;
using System.Configuration;
using System.Data;

namespace GRIDVIEW_EXCEL_FILTER
{
    public class Service1 : IService1
    {
        public FilterValueSet[] GetDistinctValue(string strColumnName)
        {
            OracleConnection connection = null;

            try
            {

                connection = new OracleConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ToString());

                string strOracle = string.Empty;
                switch (strColumnName) // This is the column name in the GridView defined
                {
                    //do something;
                }
               
                OracleCommand command = new OracleCommand();
                command.CommandText = strOracle;
                command.Connection = connection;

                command.Connection.Open();

                OracleDataReader dataReader = command.ExecuteReader(CommandBehavior.CloseConnection);

                IList<FilterValueSet> filterValueList = new List<FilterValueSet>();

                while (dataReader.Read())
                {
                    filterValueList.Add(new FilterValueSet
                    {
                        Id = dataReader[0].ToString(),
                        Value = dataReader[1].ToString()
                    });
                }
                connection.Close();

                return filterValueList.ToArray<FilterValueSet>();
            }
            catch (Exception ex)
            {
               //do something;
            }
        }
    }
    public class FilterValueSet
    {
        public string Id { get; set; }
        public string Value { get; set; }
    }
}