Oppo
Change SIM PIN auf Oppo
The SIM card PIN on an Oppo phone is managed independently from the screen lock code, inside the Security section of ColorOS. Carriers usually ship SIM cards with a generic default PIN, and leaving it unchanged is a common reason accounts get locked after a few wrong guesses on a new device.
To update it, go to Tap on Settings ➔ Tap on Security ➔ Tap on SIM card lock. On dual-SIM models, pick the correct slot first at Choose a SIM card (Dual SIM), since each card keeps its own PIN and lock state.
From there, select Tap on Change SIM PIN, then Enter the Current PIN and tap Save. You then set the replacement by choosing Enter the New PIN and tap Save, followed by Re-enter the New PIN and tap Save to confirm it matches.
This only works if the current PIN is entered correctly. Too many failed attempts locks the SIM and requires a PUK code from the carrier instead. If you only want to remove the lock screen prompt entirely rather than change the code, that is a separate toggle in the same SIM card lock menu, not this change flow.