When calling Uber, the driver and passenger can now use the registered phone number to communicate via SMS and dialing. At the San Francisco event, Uber announced the addition of VoIP capabilities to allow drivers and passengers to make calls to the Uber app. The principle of VoIP is to make voice calls through data, so you don't need to know the other party's phone number when you use it. In other words, you can make a call as long as both parties have data. Such new features are especially useful for visitors who want to roam Uber services overseas. At the same time, Uber's approach also helps protect the driver's and passenger's personal data because it does not involve phone numbers.

來源：The Verge, Engadget