Ajax Post Method

I have a requirement to use POST method using Ajax to invoke my .NET WCF JSON Service but when i tried, encountered an error,

Below is my code,

        $('#CaseInformationGrid').dataTable({
            "processing": true, // control the processing indicator.
            "serverSide": true, // recommended to use serverSide when data is more than 10000 rows for performance reasons
            "info": true,   // control table information display field
            "stateSave": true,  //restore table state on page reload,
            ajax: {
                "url": "http://localhost:61358/RetrieveCase.svc/CaseInformation",
                "type": "POST",
                "data": {
                    "User_Id": "Kannan"
                }
            },

Please help me out.

Kannan