I didn't see much of an improvement when using do not call many years ago. Enabling an iPhone app dedicated to it helped greatly. And by default on iOS I have a

I didn't see much of an improvement when using do not call many years ago. Enabling an iPhone app dedicated to it helped greatly. And by default on iOS I have all unknown calls sent to voicemail, and I just make sure to have anyone I know who expect to call my in my phone book already. So most all calls in voicemail are spam. And if I know I will be getting a call from an unknown number like to schedule a delivery I disable the feature temporarily. Process works well.