Just go and buy a prepaid sim, refill it and add the option you choose.
Take a look here:
http://www.prepaidgsm.net/forum/ital...ata-italy.html
You have to choose an option which allows you VoIP (Skype).
Customer service is usually bad if you do not speak Italian. 3 has the worst one (and you pay for it). Better with TIM and Wind.