Post: #1

There's so much confusing, conflicting or outdated information on this topic. Here's the easiest procedure. I tested this myself in January 2016.

1. Get a sim card from a newsstand (easy to find near metro stations, maybe even in the airport). Get one for the cell service provider called Tim.
2. Put it in your phone.
3. Call *144 from your phone.
4. Choose the option for english, or ask to speak to someone who speaks english.
5. Tell them your passport number when asked.
6. Done.

You can probably use a different cell service provider, but they might require a CPF number (Brazil's equivalent of a social security number) or a visit one of their stores.

Post: #2

Thanks for the info. I'm planning to travel to Brazil for the first time and is very useful for me.