OI
Name of prepaid offer: Oi cartão qualquer hora
Tariffs: (all prices include Rio de Janeiro taxes)
Local calls to fixed landlines: R$1.59 per minute
Calls to Oi (on net) mobiles to any state in Brazil: R$1.59 per minute
Calls to other carriers (off net) local mobiles: R$1.59 per minute
Roaming:
Receive calls: The company states no roaming charges within Brazil using Oi network. My personal experience it has been charged.
Data:
5 mbytes a day, for R$0.50 (send SMS with Oi to 3505).
10 mbytes a day, for R$1.00 (default offer)
15 mbytes a week for R$2.90 (send SMS with Oi to 3515)
30 mbytes a month for R$9.90 (send SMS with Oi to 3530).
All packages max speed 1 Mbps and capped to 50 kbps.
You can buy the package again as soon as it is depleted, no need to wait for the validity period to finish.
SMS:
R$0.42 per SMS sent.
They also have SMS packages which can be bought for use in a 30 period:
Pacotes de Torpedos SMS Oi Cartão ou Oi Controle
Recharge are available on most stores which accept credit cards for payment, they can usually issue electronic vouchers with the same machine, or you can buy cards at newsstands (they are not so common anymore, the physical ones).
The SIM card costs R$10.00 and comes with R$10.00 included.
You can check the balance dialing *804.
You can check the "bonus credit" dialing *805.
The mechanics in Oi are pretty hard to understand. Every month you recharge you get double the value of the recharge in "daily bonus", they give the same amount you recharged in "bonus credits" for every day of the month, so if you recharge R$20.00 you get R$40.00 daily to use in "bonus permitted expenses", the bonus can be used to call other local Oi mobiles, local Oi landlines, Long distance Oi landlines, long distance Oi mobiles, and SMS to any operator. Also these recharges must be between R$12.00 and R$25.00. You need to recharge by the 5th day of the month to get the bonus up to the 30 following days.
I really wouldn't recommend to a visitor, hard to understand and estimate expenses.