this is what i do...
Go to dial window.
Enter "##634#" number.
Input *#7284# code.
Select "Modem, USB Diag" option.
Press "OK" button.
Wait until phone restart.
tick unlock then press factory
i hope it helps
Please Wait Enter Test Mode ...
Enter Test Mode OK!
PDA SW Ver: i677UCKJ1
CSC Ver: i677ATTKJ1
Phone SW Ver: i677UCKJ1
IMEI: 359881040291783
Product ID: 7630A-AAEQMWZM-1.6.002402
Phone SN: R21C33BC55
Unlocking ...
UnLock OK !
All Jobs Done.
Total Time: 6.68 s
if still ask for pin or code
just enter 00000000
BR