I screen all phone numbers that I'm not familiar with. I give them 3 chances to leave a message. If they don't, I have the ability to block them. I figure if it's not important enough to leave a message, then I'm it's not important for me to pursue.
Also, my cell company is AT&T. They want to know about spam, nuisance or threatening texts. They have a dedicated number to send these texts to along with any other information that's related to the texts. Every time I've forwarded these texts to them, it puts an end to those texts. Please check with your cell company. And register your cell number at donotcall.gov in addition to your landlines if you have them. It takes 31 days from the date of your registration
for your registration to take full effect. All is explained at the web site.