Vivo prepaid offer is named Vivo Pré.
The offer is offered by top up value:
R$ 12.00 - R$200 calling credit good for 15 days - You can use up to R$180 to make calls to Vivo mobiles and R$20.00 to make calls to long distance to Vivo and landline phones.
R$ 18.00 - R$300 calling credit good for 25 days - You can use R$350 to call local Vivo, landline and long distance Vivo.
R$ 25.00 - R$ 450 calling credit good for 30 days - You can use R$450 to call local Vivo, landline and long distance Vivo.
Calls are R$0.89 a minute to Vivo, and R$1.25 to other local calls.
Roaming is not inclued in these offers and it is charged R$1.25 to receive calls or make calls in a different area code from subscription time.
They have higher offers, can be checked at
Recarregue e Ganhe com Bonus para DDD
To subscribe you must call *9003
Internet offer is R$9.90 a month, limited to 20 Mbytes (yes, a month), but there are no excess charges, speed is reduced to 32 kbps after quota, but you can make another top up.
To subscribe to Internet you must send a SMS with INTERNET to 1515 and the confirm the reply with SIM message (means YES, not Subscriber Identification Module).
The prepaid data offer is described here :
Para Voce Internet[]
To check balance you dial *8000 and then a SMS is sent with your current balance.