How to stop spam calls on iPhone and Android without paying for a third-party app?

Spam calls remain one of the most common mobile annoyances, despite advances in smartphone technology and network security. For years, third-party apps such as Truecaller have been the go-to solution for identifying unknown callers and filtering nuisance calls. However, both Apple’s iOS and Google’s Android platforms now include powerful built-in tools that can effectively detect, screen, and block spam calls, reducing the need for additional apps or paid subscriptions.