Three of the major phone operators (Vivo, Claro, TIM) implemented the ban, while the fourth (Oi), did not. The CEO of Vivo, one of the major phone operators, came out a couple of months ago saying that WhatsApp is "piracy", since they are not affected by the same regulations as the normal phone operator.[1]
[1]: http://www1.folha.uol.com.br/mercado/2015/08/1666187-whatsap... (portuguese)