http://www.jailbreakmatrix.com/downgrade-4.0.2
Step 11: After series of processes, iTunes will restore your device to the
required firmware.
Now, You will be finally able to jailbreak and unlock your device using our
guide posted here to jailbreak and unlock any iPhone.
但刷完后提示插入at&t的sim卡莱激活iphone....怎么弄呢?没有at&t卡..
thx!