I have had some success in just asking the spam callers to remove me from their list. I still get a fair number of calls, but they are mostly blocked by Google's filter (though they do get sent to voicemail, which results in lots of 4 second silent messages).

The last few weeks it's been spammy text messages from politicians, though.

That just sounds like you don't actually have a "do not call" list, you have something that is trying to be a "do not call" list ;)

Speak with your local politicians to fix the issues that bothers you. They don't listen, out on the streets and protest. Same way civilians communicate with their governments in every other democracy :)