Claro has the following offer on prepaid: it's named Fala Brasil R$0.25 por chamada (R$0.25 per call).
Calls to Claro phones within Brazil are charged at R$0.25 per call (every 30 minutes there is another charge of R$0.25), calls to local landlines (same area code) are R$0.45 a call (10 minutes per call limit, then another charge of R$0.45) and SMS to any operator within Brazil is R$0.45 for a day (you can send as many messages as you wish to any operator). You need to dial *525 to subscribe to the offer and a Brazilian CPF to activate the line on the first call. The offer should be confirmed by SMS. To dial to another area code you must use Claro's CSP (carrier selection code) when dialing, for example 0 21 61 9200-0000 will place a call via Claro (21) to Brasília (61) to the number 9200-0000.
Top ups for this offer are:
R$ 12
R$ 17
R$ 22
R$ 30
Prepaid internet can be chosen from two options:
15 days - 150 MB cap - R$6.90
30 days - 300 MB cap - R$11.90
To activate you must send an SMS with PACOTE to the number 767 and then confirm the offer. You must wait for the message confirming the activation of the package.
The Claro offer does not include roaming, so if you travel to another location, you are charged R$1.76 for both receiving and making phone calls, to or from any number. If you are going to change area codes within your stay, TIM is a better deal. No roaming charges.
The Claro offer for internet is described here:
Pacotes Claro
The pre paid voice and SMS plan is described here:
Fala Brasil R$0,25 por chamada
To check your balance dial *544# and an SMS with your current balance and expiration date is sent back to you.