Step 1: Open Cydia on your iPhone 4 or 3GS
Step 2: Go to Manage->Sources
Step 3: Now tap on â€œEditâ€, then tap on â€œAddâ€
Enter the following repo http://djayb6.com
Step 4: Now tap on â€œAdd Sourceâ€ then tap on Done.
Step 5: Search for â€œultrasn0w fixer for 4.3.2â€ in Cydia and install this application. This app will automatically unlock your iPhone so that you can use it with any carrier.
Step 6: Now simply restart your iPhone and voila! you should now have a fully unlocked iPhone 4 or 3GS, running iOS 4.3.2.