Yes, it is possible, but you need to find an old copy of their switchboard software. The newer one forces you to us Microtel – which is their service that resells other providers.
Older versions of the software allow you to put in your Net2Phone account # and password.
Note however that some features and advances made in the newer software you won’t be able to use. What I actually do is use the newest driver with the old software. Works like a charm (so far).