OnePlus
Change SIM PIN auf OnePlus
The SIM PIN is a security layer stored on the SIM card itself, separate from your phone screen lock. It stops someone from using your SIM in another device if your phone gets lost or stolen.
Carriers ship SIM cards with a generic PIN, often printed on the card packaging. Because that number has no personal meaning, it gets mistyped more often than a self-chosen PIN, and three failed attempts lock the SIM until you enter the PUK code.
You can replace that default PIN without turning SIM protection off. On OnePlus phones running Oxygen OS, this is handled from the lock screen security menu, not from the general SIM settings.
Menu path to change the SIM PIN
Open the Settings ➔ Tap on Security & lock screen ➔ Tap on SIM card lock ➔ Choose the SIM card (Dual SIM) ➔ Tap on Change SIM PIN ➔ Enter the current/old PIN and tap OK ➔ Enter the new PIN and tap OK ➔ Enter the new PIN again and tap OK.
You need the current PIN to complete this. If you never changed it and do not know it, check the card packaging or ask your carrier before starting, since three wrong entries lock the SIM and require the PUK.
If you only want to remove the PIN prompt at every restart, disabling SIM card lock in the same menu is the faster option, but it also removes SIM-level protection entirely.