on 10-12-2018 23:45
Solved! Go to Solution.
on 11-12-2018 04:30
Already answered by @Bambino
on 11-12-2018 08:16
on 11-12-2018 08:28
As the phone belonged to your sister when she was with O2 it needs her details to unlock.
She would have to complete the form shown in the guide https://www.o2.co.uk/help/phones-sims-and-devices/unlocking-an-o2-mobile-to-use-on-a-different-netwo...
Other than that, a mobile phone shop or market stall would unlock it for you
on 11-12-2018 08:47
OnePlus 6 (O2 & Sfr), Z3 Tablet (Three UK), iPhone 8+ (EE)