If you're on Broadband but don't use the ordinary phone modem (& it's not connected) then there's nothing to worry about, as your connection doesn't make ordinary calls. This doesn't stop diallers from installing, of course.
Previous threads via the search facility for the Helproom
If you do have an ordinary phone line / modem attached for faxing from the pc you can ask your phone service provider to bar premium rate and international numbers. This may incur a small charge, but it's a lot cheaper than having a dialler. I speak from bitter personal experience.