On the heels of Facebook’s acquisition of WhatsApp, the popular messaging service announced that it will expand into full-fledged voice calling for both iOS and Android this year. The feature will be available to BlackBerrys and Nokia devices afterwords. According to The Guardian, the voice calling will initially be free, but that will likely be temporary. Messaging is free at first but thereafter requires a $0.99/year subscription, so it’s likely that we’ll see a similar model for voice calling. Whether that will change with an eye to profitability under Facebook, however, remains to be seen. WhatsApp also released a user update: it now has 465 million monthly active users and 330 million daily users – 15 million more monthly users than even Facebook.