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I have bought a second hand phone (XS Max) which was locked to Vodafone. I have recently managed to unlock the phone but I have some worries that the original owner is has stopped paying monthly payments. Would it be possible for Vodafone to block the imei number of the phone for all networks for non payment or is that only possible for lost and stolen phones?
It's doubtful Vodafone would block the phone for non payment. However, purchasing a second hand phone is entirely at your own risk.
The first thing to do is a search of this forum where you will find some previous threads where a second hand phone has been IMEI blacklisted by the original owner..