Many of you might have unlocked your iPhone 4 with Gevey SIM, but if you are still having issues in using Gevey SIM, the site has posted an official video on how to use Gevey SIM to unlock iPhone 4 on iOS 4.0, 4.1, 4.2, 4.2.1, 4.3 with baseband 1.59.00, 2.10.04, 3.10.01 or 04.10.01 without even jailbreaking your iPhone.
Those who are unaware, Gevey turbo SIM is the only unlocking tool available till date costing around $75. Gevey SIM unlocks with jailbreaking your iPhone but if your battery drains out or if your iPhone is switch off, you need to unlock it again and if even if you upgrade your iPhone baseband you need to re-buy it to unlock.[via mobiledna]
But the big problem : Gevey SIM is illegal in USA and probably other countires as it dials 112 (emergency) then hang up.
Likely the carriers will block the SIMs that are causing the repeated emergency call hang ups, and if you change the blocked SIM many times, you yourself will get banned by carrier.