In Android N, blocking numbers is becoming significantly more effective. That's because Google is making this a feature baked into the platform. Going forward, certain apps will be able to create a list of blocked numbers, and other ones will be able to view this information.

The existing Dialer app lets users block numbers, but this information doesn't transfer to other services such as Hangouts. To prevent a number from reaching you there, you have to block them a second time.

With Android N, number blocking will not be limited to your default dialer. Google is making this a system-level task with a consistent way for apps to implement support by accessing the same list.

Only a few apps can write to the blocked number list: your default dialer, your default SMS app, and certain apps from your carrier. Service providers will also have the ability to read the list of blocked numbers and provide service-side blocking on other devices.

Even without support from the carrier, Google's list can persist across resets and devices. Users will be able to backup and restore this information like other data associated with your account.

So please stop calling already.

Source: Android Developers