I'm not sure if the ability is still around, but I know between a year and two years ago there was a fairly popular way to hack T-Mobile SD cards that people would sell quite a bit.
I never used it personally, but had a friend that did it and had it work for him.
I've only ever heard of it done for T-mobile cards, too. So there's a place to start searching further. Sorry I can't be of more help.