Call barring is controlled by your mobile network , not just your phone. Even if you swap SIMs, the barring may remain active (depending on how it was set up).

Managed by the carrier network. It applies to broad categories of calls (like all international numbers) and works even if the phone is off. How to Activate Call Barring Steps vary by device, but generally follow these paths: On Android Devices

is a telecommunication service feature that allows a user to prevent specific types of incoming or outgoing calls from being made on their phone line. Unlike "call blocking," which acts as a filter for specific, unwanted numbers (a reactive measure), call barring is a systemic restriction applied to entire categories of calls (a proactive measure).

Block entire groups of unwanted callers or create a distraction-free environment during meetings or sleep.

Managed on the device itself. You select a specific number (like a known spammer), and your phone rejects it.

Prevents the device from making any calls whatsoever.

Your phone won't receive any calls, often sending them straight to voicemail.