The Car Park Inspection: Five Checks That Expose a Secretly Locked iPhone Before You Hand Over the Cash
There's a particular kind of heartbreak that comes from getting a bargain home, popping in your SIM, and being greeted with 'SIM Not Supported'. You've bought a phone, yes — but not one you're allowed to use.
Carrier locks are the second-hand iPhone market's dirty little secret. Sellers often don't know their handset is locked; some genuinely don't care. Either way, the burden falls on you to spot it. The good news? It takes about thirty seconds if you know what to look for.
Check One: Ask the Phone Directly
From iOS 14 onwards, Apple quietly added a truth-telling tool. Head to Settings > General > About and scroll to the Network Provider Lock section. If it says 'No SIM restrictions' — congratulations, you're looking at an unlocked handset. If it says otherwise, or the section is missing entirely, proceed with extreme caution.
It's not foolproof (some older iOS versions hide it), but it's your fastest first filter. Any seller who refuses to let you open Settings before purchase is telling you everything you need to know.
Check Two: The SIM Swap Test
The gold standard, and the one we'd insist on for anything over £150. Bring a SIM from a different network to the one the phone is currently on — an old Giffgaff card in your wallet works a treat if the phone's on Vodafone, for example.
Insert it, wait thirty seconds, and see what happens. If the phone connects and makes a call, it's unlocked. If you get 'SIM Not Supported' or 'Invalid SIM', you've just saved yourself a very expensive lesson. A locked phone isn't a dealbreaker, but it should knock the price down by the cost of an unlock — often £20 to £100+ depending on the network.
Check Three: Interrogate the IMEI
Every iPhone has a 15-digit IMEI — dial *#06# or find it in Settings. Paste that number into one of the free online IMEI checkers (many UK-based services offer a basic carrier-lock status for pennies or nothing at all).
Beyond lock status, the IMEI can reveal whether the phone's been reported lost or stolen, whether it's still under finance, and even its original colour. A clean IMEI with 'unlocked' status is the green light. Anything murkier, walk away.
Check Four: Look at the Network It Came From
Some networks are simply worse than others when it comes to unlocking. Historically, EE and Vodafone handsets have carried unlock fees and waiting periods, while phones bought SIM-free or from certain retailers arrive clean. If the phone is branded with a network logo on boot and the seller can't produce evidence of an unlock request, assume the worst.
This is also where you can negotiate. A locked O2 iPhone 12 isn't worthless — but it's worth less, and a clued-up buyer says so.
Check Five: The Activation Lock Cross-Check
Strictly speaking this isn't a carrier lock, but it's the trap that catches even experienced buyers. A phone that's carrier-unlocked but still tied to someone else's Apple ID is a shiny paperweight. Before money changes hands, have the seller sign out of iCloud in front of you and wipe the device (Settings > General > Transfer or Reset iPhone). If they can't or won't, the phone isn't really theirs to sell.
Your Pocket Checklist
Print this, screenshot it, tattoo it on your forearm — whatever helps:
- Settings > General > About — check Network Provider Lock says 'No SIM restrictions'
- Bring a foreign SIM — test call before paying
- *Dial #06# — run the IMEI through a checker for lock, block and finance status
- Ask which network it came from — factor unlock costs into your offer
- Watch the iCloud sign-out — no sign-out, no sale
Five checks, two minutes, one very different outcome. The bloke at the car boot might grumble when you start poking around — but he'll grumble a lot less than you will if you skip it.
