My old carrier (a large cable company who will remain unnamed) didn't allow the "disconnected" option - one of the several reasons I dumped them. So I got in the habit of forwarding the annoying calls to a phone sex number.

I thought it was funny, of course. But most of them were robocalls with no human on the receiving end of my joke. So the robocalls continued unabated.

I stopped after I did a little research. Still not 100% sure, but it seems if one of the annoying callers actually paid for the "service" they were forwarded to, I would be billed.

Side note: I love the ability to use wildcards in the call routes. Came in handy when I discovered one of the annoying callers calls from a range of numbers.