Well, in this article i will tell you about various unlock method to unlock your iPhone along with merits and demerits
Ultrasn0w Unlock: This is a software based unlock for iPhone 4 which requires jailbreaking your device and is available on cydia.
see an example on how to JAILBREAK here.
you can jailbreak using Jailbreak me if you are on version 4.3.3, or limera1n, or green poison or snow breeze or pwnagetool.
free to download and install
only available upto iphone4 on baseband 01.59.00
unlock lost during update.
this is a hardware unlock procedure in which the Gevey SIM interposer is used to unlock the phone
Requires no jail breaking
easy to unlock
available on eBay and amazon
can unlock all base bands and firmwares
fake sims are always available
in this method the provider will take your IMEI number which is unique to every mobile devie and then the same is put into Apple's White list. so when u sync to your iTunes next time it gets permanentally unlocked
official permanenet unlcok
unlock is not lost and works exactly like factory unlock