To remove it, you aren't just changing a toggle; you are explicitly assuming financial liability. Most people don't know that O2 adheres to the GSMA (GSM Association) standard for call barring. You don't need an app or a web portal; you need the SIM application toolkit hidden in your dialer.
If you have enabled, the call barring logic changes. Your call routes through an IPSec tunnel to O2’s core network. If your account has International Barring active, the WiFi Calling server (the TAS - Telephony Application Server) drops the call before it ever hits the international gateway. how to remove international call barring - o2
O2 runs a dynamic credit check. If your billing address is new or you have missed a payment, the system auto-applies "Barring Level 2" (International). You cannot remove this yourself. You must pay your bill or call Customer Service (202 from an O2 phone). To remove it, you aren't just changing a
Call barring is controlled by specific codes. Here is the cheat sheet for international outgoing calls (code 10 or 1 depending on the handset, but typically 10 for all international except home country). If you have enabled, the call barring logic changes