You would need to plug the phone into iTunes and do a reset from there, wiping everything from the phone. I was trying that but it wouldn't work. I tried topping up the phone with more credit and that made it work again
Thanks for your example. This shows why FBI desperately needs Apple to provide backdoor to disable this feature.
This is because iPhone forgot the correct time because the battery ran out. Inserting a sim without PIN so that it can connect to the internet and get the correct time might help. Otherwise restore it from a backup.
Cheers. I got the phone working after I topped it up with credit. As soon as it connected to the 4G it started working again.