PIN lock

PIN Lock
Your prepaid SIM will be given either with: In the security menu of your phone, you can adjust the PIN code, establish one or get rid of it. But be careful doing this, as only the PUK code can release your SIM card if you have forgotten it and fail to enter it 4 times correctly.
 * a default PIN Code of 4 digits,
 * a personal code written on the cardholder or in the manual
 * no PIN at all

If it is a prepaid-only SIM which you load with small amounts of credit, you can turn off the PIN protection in your smartphone. You will probably have a bigger loss losing your device than your SIM card and getting back the remaining value abroad is nearly impossible to do. So calling the operator in this case is pretty useless.

Contrarily, when you use a SIM card on a post-paid contract or on prepaid somehow automatically linked to a payment system (like a bank account, credit card, PayPal…) it’s essential to use a PIN for protection and to block the card by calling the operator as soon as possible if you have lost it.