Visual Voicemail is a special feature that lets iPhone users view their voicemail by caller name right on the phone, without having to dial into their voice mailbox.
But how does it work? We know that it’s a collaboration between AT&T and Apple, so there has to be something from the network end that allows the iPhone to associate a certain caller’s message with their phone number (thus allowing the iPhone to see if there is a contact associated to that number).
Right now I’m using a Blackjack, but I still have the Visual Voicemail feature on my account. And I’ve noticed that every time I get a voicemail, I also get a text message (that would otherwise be an “invisible” text message on the iPhone, meaning that the user would never see it). The text message, as seen below, contains information such as my phone number, plus the information relating to the voicemail (number of caller, date and time, etc), in an encrypted form.