1. Enter your phone numbers in FTC’s DO Not Call Registry. It accepts both cell and landline numbers. https://www.consumer.ftc.gov/articles/0133-cell-phones-and-do-not-call-registry
2. For landlines, Nomorobo is a free screening service https://www.nomorobo.com
3. For cell phones, Should I Answer? Is a free app for Androids and Hiya is a free app for iPhones.
Nomorobo has an iPhone app (1.99/mo) and TrapCall ($3.95/mo) and Truecaller (1.99/mo) are available for both phones.