By following these steps, you should be able to switch off call barring on your Android device.
Some mobile carriers disable the Call Barring feature on their end. For example, if you are on a prepaid plan, some carriers do not allow you to bar international calls because they prefer you to pay for the roaming. If the options in your settings menu are greyed out or missing, contact your carrier to ask if the feature is supported on your plan. how to switch off call barring on android