Probably the 3 most popular wireless carriers in Brazil are VIVO, Oi, and TIM (at least those are the ones with stores in all the malls). I believe they have agreements with US carriers. Nextel is also making inroads here. I know if I use my AT&T chip, it associates with one of these and I can make calls, but it is costly. Since I spend half my time in Brazil, I also have a local plan and chip. One thing your friend can do is get a prepaid chip. These are available in various amounts and can have additional value added. Don't have any info on what any of this costs, just know it is possible as the daughter used the prepaid chip for a while. Unlike the US, if you receive a call on a wireless phone, you are not charged air time, so if you have the prepaid chip and others know your number and can call you, it saves.