Android
Turn SIM Card Lock On or Off auf Android
When SIM lock is enabled, Android asks for the SIM PIN before it registers with the mobile network on every restart. This PIN belongs to the SIM card itself, not to your phone, so it is separate from your screen lock code or fingerprint.
The setting sits under the security menu. Open Tap on Settings ➔ Tap on Security & privacy ➔ Tap on More security & privacy ➔ Tap on SIM lock, then use Enable or disable Lock SIM. Android always asks you to Enter the PIN and tap on OK before the change takes effect, whether you are turning the lock on or off.
Disabling SIM lock removes the PIN prompt on startup, which is useful if you restart your phone often or hand it to family members who do not know the code. Leaving it enabled adds a layer of protection if the phone gets stolen, since the SIM cannot register with a network without the PIN.
If you only want to stop other people from calling or texting on your number, check call and message blocking options instead, since SIM lock only protects against unauthorized network registration, not against someone already using an unlocked phone.
Entering the wrong PIN repeatedly can trigger a SIM block that requires a PUK code from your carrier, so confirm the correct PIN before changing this setting.