With AT&T's policy against unlocked iPhones - a move which has been in place ever since the company became the exclusive iPhone carrier when the handset was launched in 2007 - coming to an end this Sunday, users of the smartphone will henceforth be able to benefit from more affordable services while traveling overseas.

According to an AppleInsider report, AT&T has finally allowed unlocked iPhones for users whose service contract with the carrier has come to an end, and those whose accounts are in `good standing.' However, for the still-in-contract users, the advantage of unlocked iPhones can be availed after the payment of an early termination fee.

The unlocking of the iPhones by AT&T will be of notable benefit to the users who travel abroad because the move will give them the ability to use a lower-cost SIM from a local GSM wireless carrier, rather than having to foot a hefty bill for the AT&T service when overseas.

In addition, the unlocked AT&T iPhones will also work on the T-Mobile network, though it has slower data speeds than 3G. However, AT&T's unlocked phones will not work on either Verizon or Sprint because these carriers use CDMA networks which do not depend on SIM cards.

After having said in an earlier statement to 9to5Mac that it will start offing unlocked iPhones to "qualifying customers" from Sunday, April 8, AT&T has now officially announced that it is giving the customers, who have completed their two-year contracts, the advantage of unlocking their iPhone, which can then be used on any GSM network.