By default, your SIM PIN is the last four digits of your PUK. You can change your SIM PIN through your device settings. So, if you've forgotten your SIM PIN, enter a random 4-digit number, like 0000, until you're asked for your PUK code.
If you forgot or don't know your SIM PIN
Contact the carrier that gave you the SIM card. If you aren't sure which carrier to call, remove your iPhone SIM card or iPad SIM card and check the card for the carrier's name or logo. Ask your carrier to help you unlock your SIM card using the default SIM PIN or PUK code.
This is called a SIM PIN (personal identification number). Typically the user would use the GUI of the phone to enable the PIN. Some manufacturers have a default PIN value set with new SIM cards. Numbers such as 0000, 1234, or the last four digit of the cell phone number (MSISDN) are common.
Each operator has a default passcode, usually 1111, 0000, or 1234.
Generally, you need PUK number to unlock SIM when it gets locked. But luckily, there are still ways for you to unlock SIM card without PUK. You can always ask your service provider to help you after confirming your identity. And even if you fail, professional SIM unlock tools are still there to help you.
Open Settings. Tap 'General', then 'About' Tap 'Carrier lock'. If it says 'No SIM restrictions', then your phone is unlocked.
In some cases, the only thing you need to unlock your phone is a software update your carrier will push to your device, and then you insert the new carrier's SIM card and you're good to go. Or you might need to enter an unlock code provided by your current cell phone company before you can install a new SIM card.
The SIM card on your mobile phone will become locked if you enter an incorrect personal identification number (PIN) three times. You won't be able to use your phone, except for emergency calls. To unlock it you must reset your PIN by entering your SIM card's unique unlock key (also called a PIN unblocking key or PUK).
One of the less obvious substitutes for a SIM card ejector is found in your stapler. If you gently push the stapler's head, a single staple should come out halfway, without having its ends bent. Pull it out gently and use it to eject your SIM card tray.
Lost the SIM card ejector pin? Don't worry—you should be able to safely use a drawing pin, unfolded paper clip, or a similarly sized object to push open the slot and insert the SIM. With your SIM card now installed, you should be able to start making (and taking) calls and texts.
If unavailable, ensure a SIM card is properly inserted. The default SIM PIN is 1111.
The default PIN is set to 0000.
Your PUK (Personal Unlocking Key) is an 8-digit code unique to your SIM card. If you don't know your SIM PIN, you can use your PUK code to unlock your mobile and reset your SIM PIN.
PINs are not the same as passwords because they are generally tied to the devices you use.
If you don't have a SIM-eject tool, you can use a small paperclip.
If you don't have a paperclip, there are other options. Straightening a staple with flat ends works, as does cutting off the sharp point on a toothpick. Most earrings also have flat tips, so these also work great.
Pressing very hard did not help! I found the solution when I saw an enlarged picture from an opened slid: There is a spring that you have to put towards the inside of the slide. This means while you pressing the pin with reasonable pressure down, wiggle a little bit allong the length of the phone. This helped me!
Can you just swap SIM cards between phones? Yes, you can switch SIM cards between phones as long as they are compatible with the same carrier network. Your SIM card should also be compatible with the new phone in terms of size (micro, nano, and standard size).
The SIM PIN code is a security feature that protects against unauthorized individuals accessing your SIM card data. Some smartphone models come with this option on by default, while others need to have the feature enabled.