Uber had actually announced the VoIP feature back in June and has been trialing it since, but during a conference at San Francisco, the company has confirmed that the feature is now rolling out to users. It works pretty much the same way phone calls work, except that it uses VoIP which means it will rely on an internet connection for it to work.
This might come in handy for users who are traveling overseas who might prefer to buy just a data plan instead of a phone plan. It can also come in handy in situations where cell service congested or unstable and where making a VoIP call over WiFi might actually prove to be a better solution.
Uber also cites how data is generally cheaper than calls, so for drivers who are trying to cut down on their mobile expenses can take advantage of this feature instead of having to eat into their minutes.