Hi, everyone! Sorry for greeting you pic first, but given today’s topic, I could see no other way of introducing myself properly!
In Portugal (and therefore EP), we have a series of different words and expressions you can use when starting a conversation after you’ve received a phone call from someone – when performing a translation, these would all be replaced by the simple, yet powerful “Hello” (just follow the sage guidance of Adele and Lionel Richie on this one) :)
The simplest forms are Estou? and Sim? The first is nominally a form of verb estar (literally it would mean Am I?); the second, as you all know, just means Yes?
Other ways of starting a call include Estou sim? (a combo of the two); Está lá? (something like Is anyone there?). A common follow-up expression could be Quem fala? (Who’s speaking?, in the sense of Who is this?).
In Brazil, it’s very common to use Alô? as well; we used to say it more in Portugal (for example, British sitcom ‘Allo ‘Allo! is known in Portugal as Alô Alô!), but it’s not terribly common now – you may hear it every now and then, though, especially among Brazilians or people with Brazilian friends/relatives.
All of these expressions all indicate ambiguity or lack of knowledge regarding the caller; if you know who’s calling you, you’d probably simply utilize the usual expressions when you’re meeting someone in person, like Olá! and Tudo bem? (if you can be informal with the person you’re talking to; formality would require extra information, for example Está tudo bem consigo? Is everything alright with you [formal]).