A-GPS will just incurr normal data costs, there's no special rates for this. If you have a free internet allowance it will be free. The same goes for the mapping software too, there's free options like Ovi Maps and Google Maps Navigation (Android). The apps will use data to download the routes and maps, but there is no subsription charges to use the navigation software. Ovi maps does, however, have the option to pre install maps to the phone so you won't need to use a data connection to actually use the navigation.