Buying a second-hand smartphone can go wrong in two very different ways, and conflating them is a costly mistake. The first is a network lock: a carrier blacklists the handset’s IMEI after it is reported stolen or lost, cutting off calls and mobile data. The second is an account lock: Apple’s Activation Lock or Android’s factory reset protection, widely known as FRP, prevents a buyer from setting up a wiped device without the previous owner’s credentials. TechNews DevTop walks through what to verify before money changes hands, what to demand from the seller, and how to react if the problem surfaces too late.
- Check the IMEI first: Dial *#06# and compare the on-screen number with the one printed on the box or SIM tray — a mismatch is an immediate red flag.
- Boot the device in person: An iPhone showing the message that only the owner can unlock it, or an Android asking for the previous Google account, is not ready to buy.
- Know your recourse: Buyers dealing with a business have statutory conformity rights, while private sales leave far less room to recover money.
Verifying the IMEI before you pay
The IMEI is the unique identifier every handset transmits to the network each time it connects. The fastest way to surface it is the universal *#06# code; on an iPhone it also appears under Settings > General > About, and on some models it is engraved on the SIM tray. If the number shown on screen does not match the tray or the retail box, stop the transaction there.
The next step is the blacklist. When a customer reports a phone stolen or lost, the operator blocks that IMEI on its network and adds it to a blacklist shared with rival carriers so the device cannot be used anywhere in the country. The practical symptoms are telling: outgoing calls hit a busy tone, and incoming calls trigger a recorded message warning that incoming calls are temporarily restricted.
Spain has no official public IMEI lookup tool, which is why buyers are advised to ask their own carrier whether a specific IMEI is blocked before paying. Other markets show such checks are feasible: Peru’s telecom regulator, Osiptel, runs a public service on the national government portal that reports whether a handset is registered there as stolen, lost or recovered. It only covers the Peruvian registry, but it demonstrates that public verification is technically and administratively possible.
Activation Lock on iPhone and FRP on Android
Apple’s Activation Lock engages automatically when Find My is switched on. From that moment nobody can turn Find My off, erase the device or reactivate it without the owner’s Apple Account password — and a remote wipe does not remove the protection. The checks are straightforward. On iOS 15 or later, a protected iPhone displays a message stating that only the owner can unlock it; Apple’s guidance is unambiguous: do not buy it. If the lock screen or home screen appears, the handset has not been erased, so ask the seller to wipe it in front of you. Then begin setup: if it requests the previous owner’s Apple Account, the device is still tied to them. A Hello screen means it is ready to use.
Sellers have a correct procedure too: sign out of the Apple Account in Settings, then use Erase All Content and Settings. Erasing that way disables Find My and Activation Lock, though the Apple Account password may be requested. A remote erase alone is not enough. A lesser-known detail is that Activation Lock also covers individual components: a part that was protected when removed from another device does not meet the requirements of Apple’s limited warranty or AppleCare.
Android behaves similarly. Google documents that a protected phone restored to factory settings cannot be used without the credentials of the Google account previously on it, or without the screen lock. Protection activates when a Google account is added and a screen lock is configured, with some steps requiring Android 8.1 or later. The correct way to disable it is to remove the Google account before resetting. Ask the seller to delete their account and then reset the phone in front of you, or to hand it over on the welcome screen so you can complete setup with your own account before paying.
If the device is already locked
Contact the seller immediately. For an account lock, Apple notes the previous owner can remove the device from their account through a browser without having it in hand; on Android, the seller must either give access to the account or resolve it themselves. For an IMEI block, the legitimate owner is the party who must request the unblock from the carrier.
If the seller vanishes or cannot prove ownership, paid “unlock” services are not the answer: a blacklisted IMEI means someone reported the handset stolen or lost, and the problem is not technical. Buyers who purchased from a business have stronger ground. Under Spanish consumer law, the trader is liable for conformity defects present at delivery that appear within three years; second-hand goods may carry a shorter term by agreement, but never less than one year. Between private individuals that guarantee does not apply, since the rule targets businesses.
The economics are simple: the price of a used phone should include five minutes of checks in front of the seller. Anyone who refuses to power it on, sign out of their account or let you insert a SIM is revealing more than any listing ever could. And when an iPhone or Android arrives account-locked, it is above all proof that these protections work — they make a stolen handset worth far less to whoever took it.
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