SCAMMER:
My procedure for these unknown calls is this:
1. I press the mute button.
2. I Answer with my speaker button.
3. I wait to hear a voice.
4. If they hang up because they hear nothing, fine.
5. I wait 10 minutes, call back with *67 to block my number.
6. If I hear one of these telemarketing [***]-pains or scammersI make them wish they had not.
If I get a busy or "non-working" I report that to a few of the reporting sites.
Try this. If you have a better idea, feel free to share.