how the Sim card program works. is you buy this sim card for 15 bucks. you have 3 choices;
ATT (2.05gb cap/100mb a day, and on your 2nd or 3rd warning of anything over then that, termination).
Tmobile (same cap, how ever since tmo allows for 5 gb, on there network for there basic service, the warnings mean nothing, unless your obviously tethering, and throttling down to 2g service for the reminder of the month).
Hybrid (this one is really not understood too much by me, but from what I gathered, yes it roams onto both networks, how ever some people have said they get the 2gb cap on att and then get start using the tmo network for the reminder of the month) i cant see how that works but people say it does. as far as will it work in any phone, it should just as long as you have an unlocked phone and can customize the apn's (no bb though) ios devices can work too just as long as there jail broken and have "apn tweak" on them.
also an easy way for a sim card is to get a e71 from there site (if they still sell them) and then you have the sim card and a backup phone in case you brick the phone you currently have.