(Also I have what is possibly a common filtering case in the US that would eliminate 95% of my spam calls without blocking any relevant calls from "new" numbers. And for whatever reason, I have not seen it implemented anywhere yet.)
I'm in the process of open-sourcing the core part of a SaaS I run that does exactly this. It relies on Twilio but could be easily made to work with any API that exposes the forwarded number, which should be all of them.
Good luck!
Also: if (area code == my area code) AND (number NOT IN whitelist)
Basically: I have a mobile number in an area I left 15 years ago. Any call I get from there that's not one of my friends is de facto spam.
https://apps.apple.com/us/app/hiya-spam-phone-call-blocker/i...
This supports area code and local prefixes (but not wildcard local prefix). Unlike Trucaller etc., the privacy policy is ok.
If you want to block all prefixes, see WideProtect above.
Wow, that's fascinating to find out that is how the US works.
Australian mobile numbers and I'm pretty sure most of the European ones, are prefixed by carrier and have no geographical breakdown.
> prefixed by carrier and have no geographical breakdown.
I'm not sure how/if that would work here given the active mergers & acquisitions in telecom. (Among other things, some of these require some customers to be divested to achieve approval of the deal.)
Additionally, we actually had Congress pass a law requiring the ability for consumers to take their number to other carriers:
https://en.wikipedia.org/wiki/North_American_Numbering_Plan#...
Prior to this, carriers could use as leverage the fact that people prefer not to change their phone number.
For iOS: https://apps.apple.com/us/app/wideprotect-spam-call-blocker/...
If only one or a few prefixes need match, use Hiya below. If you want all wildcard prefixes, you want WideProtect.
Most do not support the wildcard formula, this does.