Here’s a solution that doesn’t require anything but what your Mobile phone already has this.
I say it as a call blocking workaround.

Assign all undesired numbers to any desired group name for eg “BLACKLIST” and assign that name an obnoxious ringtone (or silent tone).

Now if space for BLACKLIST numbers fills up, assign any new name like “IGNORE” and assign it same ringtone.

This method works fine here, on any phone brand I’ve ever owned, and with no expense or added processing load on the phone.
Good Luck!