It’s been a big week for Facebook (Nasdaq: FB), the social media giant that skipped out on the Consumer Electronics Show last week to focus on technology other than 3-D printers or smart TVs. The Menlo Park, Calif.-based social networking company introduced a new feature for its iPhone app on Wednesday that allows users to make free calls over Wi-Fi and cellular data plans.

Free calling entered preliminary testing in early January in Canada, according to the Verge, and it was successful enough to introduce to iPhone users in the U.S. on Wednesday. The Facebook app on Apple’s (Nasdaq: AAPL) iPhone smartphones now has a “Free Call” button inside the application’s friends’ page alongside the rest of their contact information.

Like the updates to Facebook Messenger introduced late last year, Facebook's free calling feature expands the company’s presence on smartphones beyond the simple application. Facebook CEO Mark Zuckerberg has never been shy about his company’s focus on mobile growth and its ambition to supplant traditional smartphone features like text messaging -- goals that exemplify the social network’s new “mobile first” slogan. In a 10-Q document filed in October 2012, the company said it expected its mobile usage rate of growth to “exceed the growth in usage through personal computers for the foreseeable future.”

Free calls are another step toward comprehensive mobile functionality entirely. Much like Google’s (Nasdaq: GOOG) Gmail “chat” features or Skype’s voice capabilities, which are  already available on smartphones, a free calling feature could turn Facebook into a rival of mobile network operations like Verizon (NYSE: VZ). If a user can send text messages (not SMS text messages, just text-based messages) and make free calls over Wi-Fi or any 3G network to any of their social network contacts, then Facebook offers all of the same services that a smartphone already does. But Facebook also has a stronger brand identity for its one-billion strong users than a service like Google, Skype, or any mobile network company can offer -- a comprehensive social ecosystem to which people are willing to surrender gobs of personal data as long as they continue to get in touch with their friends for free.

At BuzzFeed, John Hermann wrote Thursday morning that Facebook’s move into free calling shows that the company “is making moves to become your next telephone company.” But until the much-rumored "Facebook phone" comes to life, mobile networks will still need to provide data for any Facebook app to work. And like the Facebook graph search that was also introduced this week, Facebook seems less concerned with creating rival services like Google's massive search engine than it is in developing a comprehensive user-experience within Facebook itself.

If a feature like free calls takes off, Facebook may not have to become the next anything. Really, it’s going to be other mobile developers and social media companies clamoring to become the next Facebook.