Originally Posted by SubjectSigma
I'm pretty sure the cut off date for unlocking is 12w14 or 13 but either way your SOL
But the official Sony page (unlockbootloader.sonymobile) doesn't specify such a detail. I have a 12W17 R800i and I'll be trying the official method. Will report what I find.
EDIT: I tried the official method using their unlock code and fastboot and it worked! It resets your phone though and you'll lose everything other than the data on your memory card, but it's possible. Mine had a date code of 12W17.