It Hz

For this to work, two things would have to happen. 1. Make the calls legal (hang on there's more) 2. Make it mandatory that marketing agencies making the calls use a device on their phones that emits a tone or carrier when calling. Much like old military radios produce a 1k Hz tone when you key the radio; letting the other radios know there is a "call" being placed (also used to break squelch in noisy RF situations). Consumer phones would need to have a marketing block option making it the consumer choice or opt out feature. When activated, a band filter would pick up the carrier tone and block the call (if activated). Some small changes to telecom infrastructure would be necessary but in todays technology, especially since this is very old technology, it would be easily achieved.

The same tech could/should be applied to television commercials. You could choose for your tv to do any number of things from showing a blank screen, attenuating the volume by a set amount of decibels, or even change the channel.