To block unknown numbers that are not in your contacts, you can enable the "Block unknown callers" or "Silence unknown callers" option in your phone's settings. This feature will block calls from numbers you don't have saved in your contacts, preventing unwanted spam calls.
Here's how to do it on Android:
Open your default calling app.
Tap the settings symbol (usually three dots in the top-right corner).
Select "Blocked numbers".
Tap "Add a number" or "block unknown numbers".
Turn on the toggle switch or check the box next to "unknown numbers".
