I want to buy an unlocked iPhone 4s or newer but it has a bad ESN/IMEI/MEID. I read that even though it is blacklisted and can’t be used in the USA and Canada, it can be used in most of the world’s GSM carriers (assuming a compatible frequency). Assume the iPhone is GSM and the carrier abroad is GSM too. Because it has a bad ESN it’s cheaper. But I’d like to buy the phone in Canada and test it here before I leave the country so I can return it if something doesn’t work. How can I test it? I read that data might work wherever there’s public Wifi but I mean I wanna test if it can actually make calls and text. Is there usually problems with those features with used iPhones? Do any carriers abroad check the ESN blacklist and not allow the phone? I also read that some phones have a country code lock, which says that the phone won't connect to systems with particular country codes and that cracking the country code lock is a lot more difficult than the SIM unlock. Is this usual in iPhones? For the record, "bad ESN" isn't exactly a synonym for "stolen phone”.