If your phone is lost or stolen, call barring can be a temporary fix to prevent the finder from racking up huge charges before you have a chance to report the SIM as lost. Parental Control
Open the and tap the Menu (three dots/settings icon).
Call barring acts as a digital gatekeeper for your SIM card. Instead of blocking specific individual numbers (which is usually done via your phone’s software), network-level barring prevents entire categories of calls from connecting. Common Types of Call Barring on O2
The utility of O2 Call Barring spans several demographics. For parents, the ability to "bar all outgoing international calls" on a child’s phone prevents bill shock from premium-rate or long-distance dialing. For business travelers, "bar incoming when roaming" is a strategic financial tool; since many networks charge for receiving calls abroad, activating this barring ensures the user only pays for outgoing calls or data, not for unwanted marketing calls from home.