Sprint's iPhone 4S SIM unlock a limited affair

If you were planning to buy a Sprint iPhone 4S with hopes of using its unlocked micro-SIM card slot to dodge international roaming charges, that now appears to be a limited time offer.

Macworld this afternoon relays a statement from Sprint, with the carrier saying it plans to lock the iPhone 4S' Micro-SIM slot as part of an update that will go out to buyers "shortly." Those customers can then request an unlock from the carrier if they're "in good standing."

Customers could use the unlocked slot with a prepaid Micro-SIM card in order to use inexpensive local carriers while traveling. With that slot locked, users have no choice but to use one of Sprint's international roaming plans while abroad.

In essence, this means you'll need to jump through an extra hoop by calling up Sprint's customer service to get your phone re-unlocked for use of that hardware feature.

Verizon, by contrast, is locking that slot on the iPhone 4S from the get-go. It will also require customers to be in good standing for 60 days before they can call up to get an unlock.

The iPhone 4S is the first iPhone to be launched as a world phone with both GSM and CDMA hardware, allowing it to hop between the networks. That means buyers on Verizon and Sprint's network, which run on CDMA technology, can tap into GSM networks from the same device. Apple also offers a fully unlocked and contract-free version of the device for sale in a number of countries, with the U.S. getting it in November. Worth noting is that the fully unlocked version will only work on GSM networks, and not CDMA.

See also: iPhone 4S: Which is the best carrier?