ANSWER PLEASE!!!!!!!!!!! 10 POINTS PLEASE HELP!!?

ok I want to buy a palm centro off of ebay for at&t... problem is I want to use it with a prepaid sim... at&t has prepaid data plans like 100mb or what ever for $20 a month... so if I got that would I get internet on my palm centro????? also if I got a blackberry would it work on that or do u have to have a pda or blackberry plan???????????? thanks 10 POINTS!!!!!!