You won't have AT&T or Verizon's services there unless you add their international roaming as those carriers are not providers in Italy, or anywhere in Europe. If you add the roaming you should be able to use all the apps you have but keep in mind it's not that cheap. My advice would be to use Wifi only (wherever it's accessible), forget about 3G, and make calls over Skype or something similar if that's your goal.