Twice this week my daughter's iPhone 6 has locked up & said it needed the PUK code to unlock. The 1st time she had to wait for me to get home from work (scary b/c she was stuck at home all day with no phone or way to get in touch with me) & the 2nd time last night after the phone went dead & charged back up. What causes the phone to do this? I had never heard of it until the other day.
This usually happens when someone puts a lock on the SIM so that when it is removed or replaced, a code has to be entered. Its like an anti theft type option.