Xiaomi
Change SIM PIN auf Xiaomi
Every SIM card ships with a default PIN set by the carrier, and most people never bother to change it until they get locked out. On Xiaomi phones running MIUI, the SIM PIN option is managed separately from the screen lock, inside the network security settings rather than the general lock screen menu.
To change it, go to Tap on Settings ➔ Tap on Passwords & security ➔ Tap on Privacy. If you use two SIM cards, pick the card you want to update first. Then select Tap on Change SIM PIN.
You will be asked to Enter the current PIN and tap OK, then Enter the new PIN and tap OK, and finally confirm it by entering it a second time and tapping OK. The new PIN takes effect immediately and is required the next time you restart the phone or reinsert the SIM.
Be careful with the number of attempts. If the PIN is entered incorrectly three times in a row, the SIM locks itself and only the eight-digit SIM PUK from your carrier can unlock it again. If you are not confident about the current PIN, contact your carrier for the PUK before experimenting, since too many wrong PUK attempts can permanently disable the SIM.