Check the papers before you pay.
Every phone has an IMEI number. Papers ties that number to its owner. Type it in and see who owns the phone and whether it has been reported stolen, before any money changes hands.
Three possible answers. All of them useful.
There is an owner on record and no report against it. Check the seller is that owner.
Its owner has reported it. Don't pay. Walk away.
Nobody has registered it. Ask the seller to register it in front of you first.
One number. Four moves.
Register
Dial *#06#, type the IMEI, and the phone is tied to your account.
Check
Buying used? Type the IMEI. See the owner on record and any report against it.
Transfer
Selling? Offer the passport to the buyer. When they accept, they become the owner on record.
Flag
Phone stolen? Report it. Every check from then on shows it as stolen.
Whoever holds the phone.
Don't pay for someone else's phone.
One check in the market tells you if the seller is the owner on record.
Sell with proof it's yours.
A clean passport answers the buyer's first question before they ask it.
Make your phone hard to sell without you.
Report it once and the next buyer who checks sees it is stolen.
Straight answers.
Can Papers lock or track a phone?
No. It makes a stolen phone hard to sell, because the next buyer can check it.
Is my IMEI public?
The record stores a fingerprint of the number, not the number. That keeps it out of casual view, though someone determined could work a 15-digit number back, so treat it as discreet, not secret.
What if a thief registers it first?
The first claim wins, so register a phone when you buy it. The passport shows how long each owner has held the phone: a brand-new owner with no history is a warning sign.