Major cell phone carriers tend to offer some sort of spam detection service, and some will even block such calls for you. Generally, pay-as-you-go customers don't have access to these programs, though that does vary by carrier.
Here's a roundup of the four major carriers in the USA:
AT&T offers Call Protect, which offers a free version. The plus version, which offers caller ID with location data, starts at $3.99 a month.
Sprint offers a Premium Caller ID for $2.99 a month, but it cannot block spam calls. Gah.
T-Mobile identifies spam calls for you without the need to download anything. You can also activate Scam Block, free, to stop spam calls from even ringing on your phone.
Verizon offers Call Filter, which is included on Android phones and is a free download for iPhones. This app filters out spam calls. The premium version, which offers caller ID and a personal spam list, starts at $2.99 a month.
Stop Spam Calls on iPhone and Android Using Third-Party Apps
A variety of third-party apps can identify and even block spam calls. Here are a few popular options:
Truecaller runs on Android and iPhone, is free, and is generally well-reviewed. It asks for access to your contacts, which is used by the company to build a phone directory.
Hiya runs on Android and iPhone, is free, and is also generally well-reviewed.
RoboKiller runs on Android and iPhone, requires a monthly subscription starting at $2 a month, and also hilariously wastes the time of spam callers using a combination of AI and pre-recorded messages. You can even listen to the recordings of spammers being trolled if you want a little bit of payback. RoboKiller offers a seven-day free trial.
Nomorobo is free for some landlines and costs $2 a month on Android and iPhone.