Apple has fixed Activation Servers and hence SAM iPhone unlock will not work.MuscleNerd of iPhone-Dev Team has tweeted that SAM unlock is no longer working.
for the next few hours, trying SAM on new SIMs will probably be hit or miss, but eventually it will be all “miss”
For those who have have unlocked iPhone using SAM unlock should backup using latest version of Redsn0w.
There are reports from iJailbreak also that SAM iPhone unlock is not working as the guys have tried but had no luck activating SAM unlock on an unofficial SIM card.
Keeping backup of Activation Tickets will help in future unlock of iPhone.