Have you ever received a call from a Brazilian and they ask YOU 'Quem ta falando?' or "Quem e?". When I first got here, picked up my phone and was asked who I was I use to be so confused - I thought it was one of those trick phonecalls when two calls were made and then put together and no one would be able to work out who was calling who, and why.
Then I realised it was just a standard greeting on the phone... even if you know who you are calling, and it's 99% most likely that they are the one to answer the phone you still ask the person you called - Who is speaking?
I tried to get an explanation from my Portuguese teacher and she said, people like to check they have called the right number but I still don't understand why you wouldn't ask "Would I be able to speak to so-and-so?" (sounds much more polite!). I guess this is one of the other Brazilian things I will get use to over time!!
I guess it's a good tip for Brazilians who travel overseas - when you make a phone call, don't just say 'Who are you?' - it would be considered very rude!