At&t standard media net on an old smartphone?

i have a blackjack 2 that i bought from them over a year ago, and i have upgraded to a new phone now with them and have the family unlimited text and the 10 dollar standard media net. I want to start using my old blackjack again but i dont want to pay the 30 dollars which is ridiculous for what i use the media net for. i am only 16 and use facebook and myspace and the occasional youtube. so if i put my sim into my blackjack again will they auto add the PDA plan or send me a message or call me or something, and if they do i will just pop the sim back into my other phone make a call and say they are making a mistake. will this work?