For a little bit more then a year my Internet Service Provider (ISP) is the São Paulo based "Directnet (Neovia)" and provide internet by a WiMax system to São Paulo and some surrounding cities. They promise a good service, ...
I am thinking in changing to another ISP because they have a very bad service. My connection is unstable and has a lot of time outs, the speed varies a lot from 10 KBs to a maximum of 59KBs. If the connection drops and you call their help desk they say it´s your computer or network card that has problems, the problems never come from their side. I stopped calling their help desk because you pay a fortune to stay on the phone and for them to come to the conclusion that it is not their fault but that something must be wrong with your computer.

My advice: Do not take Directnet / Neovia as your Internet Service Provider (ISP), look around and see what the options are in the region where you live!