This app was mentioned in 6 comments, with an average of 0.17 upvotes
Might I also suggest a mobile security app with spam call alert like Norton mobile security. I have this app and it will occasionally alert me of a possible scam calls with various options to block numbers not in my contacts along with unknown numbers and frequently declined numbers. I also have the T-Mobile scam block activated as well.
Try the 30 day free trial and see if activating the scam options help any https://play.google.com/store/apps/details?id=com.symantec.mobilesecurity
Spam and Fraud Call Alerts helps you identify known robocall numbers with schemes devised to trick you into providing your personal information. You can choose to block these calls.
★ Call Blocking allows you to automatically block calls from specific phone numbers or anonymous or unknown numbers (smartphones only).
If you do have success with the app, I purchase the yearly subscription through eBay for around $8 and can link you too the vendor I purchase from. Good luck
Norton Security and Antivirus
https://play.google.com/store/apps/details?id=com.symantec.mobilesecurity
Can you believe iPhone users don't have antivirus software? They think that just because iOS doesn't have the same high-quality levels of malware that Android does that they don't need it.
Wake up iSheeple!
It blocks anyone from accessing your phone number or personal information stored on your phone I'm pretty sure.
https://play.google.com/store/apps/details?id=com.symantec.mobilesecurity
lame excuse you say?
https://play.google.com/store/apps/details?id=com.symantec.mobilesecurity&hl=en
go find an app that does the same on iOS.