Has anyone had the $30 data plan added to their Oct. AT&T bill after using an unlocked smartphone after 9/6/09?

Has anyone incurred the mandatory $30 data charge for AT&T after using an unlocked smartphone on their October 2009 bill (whether it was previously on AT&T's network like the Blackjack II, for example, or if it was an international GSM phone compatible with AT&T's network). I'm looking to upgrade from my nokia 6555 (a mid-range phone) to a used Samsung Blackjack II smartphone, while keeping my basic phone in case AT&T catches on to my SIM card switching tricks. I just want to know if AT&T was able to detect anyone doing this similar plan easily.