How To Fix The iPhone Message “SIM is locked”: Warning – DO NOT GUESS YOUR PIN

This is one of those obnoxious errors that will pop up unannounced, and usually at the most inconvenient of times. This well intended security feature can leave you in a predicament. Luckily emergency calling is still enabled. Unless you’ve assigned a pin code to your SIM you are now locked out from making any phone calls. There are two easy fixes, one of which may require you contacting your service provider.

The idea behind the SIM pin is to serve as added security to prevent an unauthorized user to use your phone to make calls or use you internet access.

Lock your SIM card with a PIN (personal identification number) so that an identification code is required for phone calls and cellular data usage. To stop other people from using your SIM card to make phone calls or use cellular data, you can use a SIM PIN.Oct 2, 2021


There is a huge warning with using the SIM pin lock function. If you forget your pin, you risk permanently locking your SIM card. In the case where your phone uses a physical SIM that will mean a trip to your carriers’ retail store and acquiring a new SIM card. If you lock yourself out of the newer eSIM you may be in luck provided you have access to another device on your account – a simple phone call may resolve the issue. If there is any doubt, read no further and call your carrier.

Attribute: Support

If you are adventuresome and accepting all risks, before making that call you can try the default pin code – which some carriers leave at the default: 1234. If that does not work you will have no other choice, you will have to phone your carrier and request the “SIM unlock pin code and/or PUK code” (some devices will prompt for the PUK instead of the pin). Simply input the requested code and you are back in operation, but don’t stop there.

To ensure the SIM lock does not leave you stranded again, consider turning off the sim lock. The SIM lock/unlock is found under Settings –> Phone –> SIM Pin and then simply turn off the SIM Pin (from “green” to “grey”).

It would be a good idea to reboot before hanging up with your carrier’s technical support line just to ensure that the SIM lock does not come back on. Do note, this has nothing to do with your carrier (while they are usually the ones left with assisting you) and everything to do with Apple updates. It appears Apple Updates triggers the SIM lock to be turned on for some unknown reason. This latest occurrence is being reported with the 15.3.1 update. End-users have noted this same bug with iOS updates 12.b.2(?), 13.4, and 15.1 updates. It would seem as if it can occur with any of the updates as it clearly hasn’t been resolved. If the default 1234 pin code doesn’t work, give your carrier a call they should be able to assist you (you should have two more tries). Be sure to ask for tech support – otherwise you are probably speaking with a “gen care” agent that isn’t always capable / trained in such matters. If all else fails you can try to call Apple Care Support at:

  • (800) APLCARE
  • (800-275-2273)

Per Apple Support to turn your SIM pin on or off:

1. If you have an iPhone, go to Settings > Cellular > SIM PIN. If you have an iPad, go to Settings > Mobile Data > SIM PIN.

2. Turn on your SIM PIN or turn it off.

3. If asked, enter your SIM PIN. If you’ve never used one, enter the default SIM PIN from your carrier. If you don’t know what the default SIM PIN is, don’t try to guess it. Check your carrier’s customer service page or the documents that came with your wireless plan. Or you can contact your carrier.

4. Tap Done.

Per Apple Support Documentation

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