This app was mentioned in 3 comments, with an average of 120.33 upvotes
Regex number blocker.
https://play.google.com/store/apps/details?id=com.budaloop.regexblocker
I kept getting calls from different numbers that all matched a pattern. They all came from (xyz) 555-01ab, where all the letters could be random. Answering the phone have me dead air.
So I wrote this app to stop that. The UX is not the best, but it does what it's supposed to.
Yes this is a shameless plug, I wrote the app. I have about 80 users and wouldn't mind more. I don't think I've made more than 50 cents off ads.
I use this to block such calls:
https://play.google.com/store/apps/details?id=com.budaloop.regexblocker&hl=en_US
Some dev clearly made it in like 2 days, but I'll be damned if it doesn't work like a charm.
They seemed to have stopped, but if I get called again I will. Essentially what happened was on their first call I picked up and heard this really fast spanish robocall that wasn't spoofed. The next day I got the same call from a different number. Same sounding voice and everything. And a different number. Both spoofed. So I tried seeing if there were any apps that would just block numbers by RegEx + whitelisting. I didn't find any but what I did find was something that told me the first number that wasn't spoofed came from a cigar place, and I do know where it is nearby, and I do know that if they continued I probably could try to do something. I know someone who speaks Spanish but I haven't recorded the call, and while I know a bit of it, I don't know enough to say without doubt that it was this specific cigar store, or any in particular.
If you use an Android device this seems promising. https://play.google.com/store/apps/details?id=com.budaloop.regexblocker&hl=en
Unfortunately like I said earlier I couldn't find any that support a whitelist, and a lot of people I know have numbers with the same first six digits that the the robocalls spoof, so whitelisting couldn't work. I just now found this though: https://play.google.com/store/apps/details?id=dmate.callfilter.keyapp
It seems promising but I have no experience with it and it isn't free.
What I was planning on doing with a hypothetical phone number blocking app that supported regex and whitelisting would be to block all phone numbers that started with my the same first six digits as my phone number except for those on my phone number using regular expressions.