OnePlus
Enable or Disable Fixed Dialing Numbers auf OnePlus
Fixed Dialing Numbers (FDN) is a call restriction stored directly on the SIM card. Once active, the OnePlus phone can only dial numbers saved in the FDN list, and every other outgoing call gets blocked immediately.
The feature is managed through the OxygenOS call settings, not through Android's general permission system. That is why FDN survives a factory reset: the list and the lock both live on the SIM, not in the phone software.
How to turn FDN on or off
Open the Phone app ➤ Open the menu ➤ Open the Settings ➤ Tap on Call accounts ➤ Choose a SIM card (Dual SIM) ➤ Tap on Fixed Dialing Numbers ➤ Tap on Enable FDN ➤ Enter the PIN2 and tap OK.
To switch it off again, repeat the same path and disable the option with the same PIN2. On dual-SIM OnePlus phones, FDN is set per SIM slot, so check the correct card if only one line is affected.
PIN2 is a separate code from the everyday SIM PIN and comes from the mobile carrier, not from OnePlus. Entering it wrong repeatedly can lock the SIM permanently, so confirm the code with your provider before testing this setting on a live SIM.
FDN suits parental control or company phones with a fixed set of approved contacts. For blocking a single unwanted caller, a normal block list in the Phone app works faster and does not need PIN2.