Apple on Monday seeded a third beta of iOS 9.3 to its developers. The software is available to members of the Apple Developer Program and can be deployed on the iPhone, iPod touch and iPad devices running a prior beta as an over-the-air download in Settings → General → Software Update.
A standalone installer should be available shortly through Apple's portal for developers.
The new beta has a build number of 13E5200d and adds a new Wi-Fi Calling option for Verizon customers. iOS 9.3 beta 3 arrived approximately two weeks following iOS 9.3 beta 2 and a full month since the original 9.3 beta was seeded to developers. We will update the article with a running list of enhancements in the new beta as we encounter them.