I'm sorry to hear that you are being treated that way. It's unfortunate that they don't value your properly and it's not right. Whenever greedy corporations can take advantage of people they do, while the executives make a fortune. I wish I had some great advice, but never having worked in Brazil I'm not an expert!
You might consider changing companies and leveraging a potential exit to your current employer for better pay.
Yes, I have been looking for other opportunities around here, but let's say that my field is pretty much slave labor.