I need advice on purchasing a new prepaid phone

recently the site where i buy my minutes locusmobile.com sent me a phone for free because my former phone was not gsm. This phone was a Seimens A56 and because it was cheap, (don't think they would send me an expensive phone for free..LOL) it only lasted a few months.
I want to buy a new cell phone(prepaid). But i still want to keep my same phone number. I was told that the sims card has all that info on it and i need to buy a prepaid phone that is AT&T (formely Cingular) compatable as my sims card will only fit AT&T compatable prepaid phones.
My question is this... What AT&T compatable prepaid phone or phones are similar to Siemens that my sims card will work?

that pretty old, try something a little newer

my be a nokia 6030 or motorola phone