You should explain why that number is critical, what happens before, what happens after.
All kinds or rules here https://www.consumer.ftc.gov/articles/0198-telemarketing-sal...
The robodialers are so stupid, though. They don't want to pay for the second 6 seconds, and will hang up quickly. So intermediary companies keep the calls open to keep their stats good, then charge the dialer guys more.
Telecom is filled with actors that can't handle basic algebra.
Source: I've run billions of calls as a VoIP network and consulted for folks doing dialer.
I see things like this in telecom too much. Where people are mathematically going to lose, guaranteed, but prefer a certain billing because it's easier to understand, or looks cheaper. While this is understandable for an SMB that isn't in the telecom business, I've seen big names take these same deals. And I've seen the other end: they 100% are losing a few % in doing so.
The "say nothing" is the important part here I think. Most robocall systems would wait for some kind of voice before starting their spam and that's the point where they probably mark the number as 'legit', not as soon as you pick up as they don't know if it's an actual person that picked up.
It might just be a trick that people pass along regardless of effectiveness.
Actually I like the idea of fining people into bankruptcy so I don't have to deal with their nonsense. This is literally the basis for paying taxes. If I have to do my own guerilla defense against robocalls it's literally a waste of my time, so I typically let calls go to voicemail instead.
Fwiw this hasn't worked with the calls that I get (landline) which start out with what sounds like a fax tone at the start (but is definitely not a fax machine).
A lot of people deal with robocalls incorrectly by declining calls from unknown numbers. Don't do this.
The correct solution is to answer the call, say nothing and hang up after 3 seconds.
If it's a real call you'll hear background noise most of the time or the caller will say "hello?" Or they'll call back thinking something went wrong. Most robocallers are programmed to do nothing until they hear a voice.
But the critical part of all this is hanging up within 6 seconds. This is the one thing that hurts the telco knowingly supporting this. If a telco has too many such calls they essentially get punished as a bad actor, which is why they need legitimate traffic. I think robocallers and their telcos have wished up to this as I suspect they'll stop calling you if you do this.
When I started this I got 2-3 robocalls a week. Not a huge amount but annoying. Now I think it's been at least 2 months since I've gotten one. It could be that crackdowns on robocalls are yielding results but I'm not convinced.