that is the same version we are using.
the problem you are facing has nothing to do with Telerik.
to be able to support Ajax you need to put the following in your code
<asp:ScriptManager ID="ScriptManager1" runat="server">
then to make web service call do something like this
PageMethods.[your server side function name](parameters,
CallSuccess, CallFailure, JSParameters);
on server side you need something like this so your AJAX can call it
public static string your server side function name(string some_variable)
//do some work;