Any particular reason you want the software? If the ISP's changed their service, it is likely that alot of things, such as the dial-in numbers, DNS has also changed. If that being the case, the software more than likely will do nothing for you, except sit there taking up space. Using software from a free ISP, which has switched to a paid service is not going to get your free serivce once again. Lots has changed now, even if the software connected and somehow where to you get you "freely" connected to their service, with the Caller ID service, you can be sure to be charged on your phone bill for using the service.
If you have other reasons to want the software, that might be of interests to other members, you should give some tips for its useage. maybe someone else can benefit as well.