Don't get me started on XM. Starting the second year after I bought a car they were calling me several times a week. It took a few years of "No" and blocking any number in my area code that isn't in my contacts (my phone number is not local) for it to stop. Then I brought my car to the dealership to have some recall handled, and the calls have started again....

I wonder if you'd get put on a block list if you answer the call but play a train horn into the phone every time instead of talking

That sounds like it would primarily impact the low-paid worker on the other end of the line rather than alter company policy.

Instead I suggest playing back a pre-recorded sales pitch for a relevant trade union: The workers won’t suffer from bleeding ears and the bosses might actually care.