this is the plan http://www.walmart.com/ip/Tmobile-30-Wireless-Airtime-Card/15443357?tv2=true& They say its 4g though but can I use my iPhone 3g on it? i don't care if its a little slow
You could but don't expect 4G speeds. In this case even 3G speeds probably wouldn't happen cause of T-Mobile's incompatible 3G/iPhone network so expect 2G.