The phone often receives unwanted calls from unknown numbers. True callers are spam calls. Such calls are annoying during busy times. But there are ways to control these unwanted calls. Just change a few settings on your phone and stop receiving spam calls.
How to block spam calls
True Caller: True Caller is a very popular app for blocking scam calls on Android and iPhone. In this app, when a call comes from an unknown number, the real identity of the number is immediately informed. Basically, True Caller stores the numbers saved on different phones in their database. This information is then provided to customers, so that unknown numbers can be easily identified. True Caller automatically blocks many scammers. It is also possible to block specific numbers.
Robo Killer: When someone calls you and the number is verified as spam in RoboKiller App database, the call will not go through to you. Instead of a call, the phone will get a message to block the number. The difference between this app and other apps is that the app can reply with pre-recorded messages. A 7-day free trial is available on RoboKiller. Later, the service has to be purchased for $4 a month or $30 a year.
Heart: Hiya will help you block messages from exactly the numbers you want to avoid. Other services of this app include call block, blacklisting of unwanted numbers, information about incoming calls and providing spam alerts.
Apart from apps, mobile phones also have several built-in features to block calls or numbers.
References: Mashable, Android Police