Re: is it neccassary to use a pre paid phone card for internet use
It might make it cheaper to make international calls than using the phone to make the call directly (if you have unlimited voice, you're calling a local number as far as the carrier is concerned - and you're paying the card supplier for the international call) - but it's not for internet use, only for voice use.
For internet use you need either a cellphone account (which you do for using a phone card anyway) or wifi.