I saw a television news reporter recommending this free app the other day, tried it and it works very well. It's called Hiya.
It was originally developed as a Caller-ID app for Whitepages. In February 2016, Hiya reached a deal with Samsung to integrate its caller profile and spam protection services into all Galaxy S7 and Galaxy S7 edge phones in 16 countries. The company extended its partnership with Samsung in a separate deal in August, 2016 to include its service on the Galaxy Note 7 and to expand the partnership to a total of 28 countries.
In 2016, Hiya launched Hiya Cloud, its network level caller ID and call-blocking offering. After offering only a limited version of its app for iPhones, Hiya later announced that the full version of its app would be available on iOS 10. Soon after Hiya began providing spam protection services to AT&T phones through the AT&T Call Protect product. In 2017, Hiya entered a similar partnership with ZTE to provide call spam protection services for all Axon 7 users.
Hiya has a database of 1.5 billion phone numbers that it draws from to identify the source of incoming calls which helps users make a decision about whether or not they want to pick up a call from an unknown number.
The service can automatically block calls from numbers that it has deemed to be associated with fraud and notifies the user of the blocked call. In some cases, the app will let the call go through but notify the user that the number is suspected of being spam.
Users can report numbers associated with unwanted calls through the app well as well as block future calls from certain phone numbers.