They say if you answer spam phone calls it doesn't help because now they know the number is good. But if you let it go to voicemail, they still know the number is good. So instead I now answer on mute and then just mash the keypad. Longest anyone has stayed on the line so far was four seconds. Feels like the number of calls is decreasing lately too but hard to know...
Easier and probably more annoying than yelling at them, and with any luck they think it's a machine and take me off their list!