AT&T announced last week that it would finally allow out-of-contract customers to unlock their iPhones and use it on another carrier.

Beginning Sunday, April 8, we will offer qualifying customers the ability to unlock their AT&T iPhones, read a statement issued by the carrier.

The only requirements are that a customer's account must be in good standing, their device cannot be associated with a current and active term commitment on an AT&T customer account, and they need to have fulfilled their contract term, upgraded under one of our upgrade policies or paid an early termination fee.

As noted by iDownloadBlog, users need to place a call to AT&T or have a chat with them online to start the process. After collecting some basic information from you, AT&T will take its sweet time (72 hours to 2 weeks) to verify you are indeed [eligible] for unlocking your iPhone.

After approving the user, AT&T sends an email with instructions to complete the unlock.

However, there's a glitch. Users, who care about their jailbreak, might not be able to unlock their iPhone without losing the untethered jailbreak on their device.

iDownloadBlog has shared a process to unlock the iPhone without having to restore or lose the untethered jailbreak:

Step 1: Download the latest version of RedSn0w, available here.

Step 2: Plug the iPhone in and follow the steps to put it in DFU mode. To know how to put the iPhone in DFU mode, click here.

Step 3: After RedSn0w recognizes the iPhone, select Jailbreak option.

Step 4: On the following screen, deselect Install Cydia and select Deactivate.

Step 5: The device will have lines of codes running on the screen, which is normal.

Step 6: Wait until the device reboots and then launch iTunes. iTunes will then give a message saying that the iPhone has successfully been unlocked.

[Source: iDownloadBlog]

For users who travel overseas, an unlocked iPhone is ideal as they can use a cheaper SIM card from a local GSM wireless carrier, rather than paying for expensive service from AT&T, PCWorld reported.

The report added that Unlocked AT&T phones will work on T-Mobile's network, though data speeds will be slower than 3G. In addition, AT&T's unlocked phones won't work on Sprint or Verizon, due to their use of CDMA networks that don't rely on SIM cards.