If you want to be able to call web services through an ajax call via jquery, you can use this little piece of code:

$.ajax({
   url: "yourwebserviceurl",
   type: "GET" //the http request type,
   dataType: "json" //the expected data type returned by web service
   success: function(response) {
      //do something here with response object if call goes OK
   },
   error: function() {
      //do something here if call goes KO
   }
});

more informations here