Samsung
Change SIM Card PIN auf Samsung
Carriers often ship SIM cards with a default PIN such as 0000 or 1234. Your Samsung phone stores this PIN check as a security layer on the SIM itself, separate from your screen lock, so changing it does not affect how you unlock the device.
The setting lives under the SIM card lock menu, which also lets you require the PIN after every restart. To change it, you first need the current PIN, then confirm a new one twice.
Tap on Settings ➔ Tap on Biometrics and security ➔ Tap on Other security settings ➔ Tap on Set up SIM card lock ➔ Choose a SIM card (Dual SIM) ➔ Tap on Change SIM card PIN ➔ Enter the current PIN and tap OK ➔ Enter the new PIN and tap OK ➔ Enter the new PIN again and tap OK
On Dual SIM phones the two SIM slots have independent PINs, so repeat the steps for the second card if it also has PIN protection enabled. If you enter the wrong current PIN too many times, the SIM locks and asks for a PUK code instead, which you get from your carrier.
Changing the SIM PIN only makes sense if SIM card lock is already active. If it is off, activate it first from the same menu before you can set a new code.