People on XDA have been doing this fine perfectly for years without any trouble.I just now went to the ATT website store to buy the SGS2 and it popped up 1 warning saying that the SGS2 requires a data plan, 1 warning that the iphone unlimited data plan was not compatible, and 1 warning that if I switched plans I could not switch back. It also had a message saying 50% of data users use less than 200 mb, and 94% use less than 2 GB. So at least it is nice that they are being upfront and clear about the matter.
I assume the reason why I can't keep the grandfathered plan is because it is only compatible with iphones...
Call an AT&T rep.
