The Federal Trade Commission offers the following advice:
Scammers can use the internet to make calls from all over the world. They don’t care if you’re on the National Do Not Call Registry. That’s why your best defense against unwanted calls is call blocking and call labeling. Which type of call-blocking or call-labeling technology you use will depend on the phone — whether it’s a cell phone, a home phone that makes calls over the internet (VoIP), or a traditional landline.
They have a Web Page located here: https://consumer.ftc.gov/articles/how-block-unwanted-calls
Blocking calls on a cell phone is covered there, but the summary of that advice is:
Call Blocking app
One of the best ways to block unwanted calls on a cell phone is to download a call-blocking app. A call-blocking app acts like a filter. The company behind the app uses call data or reports from users, the FTC, and other sources to predict which calls are illegal or likely scams. The app then intercepts those calls before they reach you. Some apps are free, but others you have to pay for.
Check the built-in features of your phone
Many cell phones come with settings that let you block calls from specific numbers, though there might be a limit to how many numbers you can block. Cell phones also typically have features like Do Not Disturb, where you can set hours during which calls will go straight to voicemail.
See what services your phone provider offers
Check your phone provider’s website or call customer service to find out what call-blocking or call-labeling services it offers or recommends. Some services are free, but others might charge you a fee.
For links to company-specific information about blocking calls, go to the FCC’s Call Blocking Resources. https://www.fcc.gov/consumers/guides/stop-unwanted-robocalls-and-texts?from=home#call-blocking-resources