Before you can switch carriers or use a local SIM while traveling, you need to know if a locked SIM card is the problem, but "SIM locked" actually describes two different issues. The first is a carrier-locked phone that restricts which network you can use; the second is a SIM card locked by a PIN code that prevents access to the card itself. If a PIN prompt is blocking your service, you will need your finding your SIM card pin to regain access. This guide helps you identify which situation you're in and explains exactly how to check and resolve each one.
Is your SIM card locked? Two different problems
A carrier lock is placed on the phone itself, not the SIM card. This restriction is typically applied when a phone is purchased through a carrier with a contract, payment plan, or at a subsidized price, to keep the device tied to their network. A SIM PIN lock, on the other hand, is a security feature you (or someone else) enabled on the physical SIM card. Entering the wrong PIN three times triggers a PUK code requirement, which locks the SIM until the correct code is entered. Knowing which type of lock you're dealing with determines the next steps.
How to check for a carrier lock on iPhone
Checking an iPhone for a carrier lock takes only a few taps. Go to Settings > General > About. Look for "Carrier Lock" or "Network Provider Lock." If your iPhone shows "No SIM restrictions" next to "Carrier Lock," it is unlocked; otherwise, if it says "SIM locked" or lists a specific carrier, it is locked. Apple cannot unlock your iPhone for use with a different carrier; this service can only be provided by your current carrier.
How to check for a carrier lock on Android
The method varies by manufacturer, but the principle is the same: see if your phone can detect networks other than your current carrier's. For Google Pixel devices, go to Settings > Network & internet > SIMs, select your primary SIM, and toggle off "Automatically Select Network" to see if multiple carriers appear. For Samsung Android devices, go to Settings > Connections > Mobile/Cellular network > Network operators, then toggle off "Select automatically" to check for multiple available networks. Some Android devices may also show a "Network lock status" under Settings > Connections > More connection settings or "SIM Status" under "About phone." Samsung does not lock its devices to any particular network; any network lock on a Samsung phone is imposed by the original service provider or retailer.
How to check for a SIM PIN lock
A SIM PIN lock is easy to spot. When you power on your phone or restart it, a prompt appears asking for the SIM PIN before the device connects to the network. If you don't know the PIN, you can try entering it, but three incorrect entries trigger a PUK code requirement. At that point, the SIM card is locked and you cannot use the phone until you enter the correct PUK code.
How to unlock a carrier-locked phone
Only the original carrier that locked the phone can unlock it. Typically, a phone must be fully paid off and not reported as lost or stolen to be eligible for carrier unlocking. Contact your carrier to request an unlock; they will verify your account and eligibility before processing the request. Once unlocked, you can use any compatible SIM card from another carrier, but you'll first need to know how to access the SIM tray by locating the SIM card on Android phones. For a detailed walkthrough of the entire unlocking process, including how to submit your request and what to expect, refer to our comprehensive unlocking guide.
How to unlock a SIM card with a PUK code
If a SIM card is locked due to entering the PIN incorrectly three times, a PUK (Personal Unlocking Key) code is required to unlock it. The PUK code can usually be found on the original plastic card that contained the SIM, or it can be obtained from your mobile carrier. When you get the code, enter it on the prompt that appears after the failed PIN attempts. After entering the PUK code successfully, you will be asked to set a new SIM PIN. If you are inserting a SIM card into a new device and encounter this lock, the same process applies, find the PUK code from your carrier's documentation or support team, then follow the on-screen instructions to regain access to your network.
