If you’re itching to get rid of your old smartphone to switch to a new Windows Phone, you’re in luck: Microsoft is currently holding a trade-in promotion for owners of Apple’s iPhone 4, 4S, or Samsung’s Galaxy S2. If you own one of those phones – and they’re in relatively good condition with the original accessories – Microsoft will give you either a Lumia 1020 or Lumia 1520 for free, with the signing of a two-year contract on AT&T.

There’s one kicker to the deal: it’s only available in Microsoft’s retail stores. Considering that there are only 63 Microsoft Stores currently open in the world, it’s likely that not many customers will be able to take advantage of the offer – and maybe that’s why the offer exists in the first place.

Still, if you’re looking to cash in on a fantastic deal for a free flagship phone with AT&T and you live near a Microsoft Store, this deal can’t be beat.

[Microsoft Store via BGR]