(Note: Actual codes vary by carrier; modern smartphones have a UI for this in Settings > Mobile Network > Call Barring.)
Call barring is a service provided by your mobile carrier or landline provider. When activated, the network intercepts calls before they even reach your device (for incoming) or before they are placed (for outgoing). It is typically secured with a (often 0000 or 1234 by default) to prevent unauthorized changes to your restrictions. Common Types of Call Barring
Call barring is a useful feature that allows users to control the types of calls they make and receive on their phone. By understanding what call barring means and how it works, users can take advantage of this feature to prevent unwanted calls, control spending, and increase security.