Apparently it's pretty simple, but I've met many platforms disable the PIN(Personal Identification Number) to a SIMs. on iPad it gives them headaches.
For iPhone, disabling is somewhat more intuitive in the menu. As the option is available Phone Number. On the iPad things are a little different, because the iPad does not have this option in the Settings menu. The iPad can not be done GSM phone calls, even if you have a SIM that supports LTE / 4G and GSM.
Deactivate the PIN code of a SIM card on the iPad (valid on all models - iPad Air, iPad Mini, iPad Pro)
Every time we reboot the iPad or reintroduce a PIN that has set a PIN, it is requested immediately after the device has been authenticated and unlocked.
It is recommended to keep this code active, which may prevent unauthorized use of the subscription or prepay card in case of loss or theft of the device. If you do not want to keep this active code, you can disable it by following these simple steps:
1. We're going to the menu Settings ? Cellular Data ? Cellular Data Options.
2. In the "Cellular Data Options" menu, the last option at the bottom is the one that helps us to disable the SIM card PIN in the iPad.
3. Under the “SIM PIN” option we have the options to deactivate / activate PIN or change PIN code for SIM card in iPad.
To make a change here, you need to know the PIN of your SIM card. If you do not have this PIN, your recovery can be done using the PUK code. SIM card unlock code.