I got this plan last November. As of last November, it required a SIM from either, get this, Walmart, or 1-800-TMobile. You can't use a SIM from a T-Mo retail store. You can't buy a SIM from Walmart, but you can buy a $20 T-Mo phone and use the SIM from that. But don't activate it, until it's in your smartphone. Or you can get the SIM for $5 from 1-800-TMobile.
Also, check out the plans details closely. They don't mention it, and the 1-800-T-Mobile CSRs won't tell you, or don't know, but you can't tether on this plan, at least, not if you're using the Samsung Galaxy SII and probably not with any/most Tmo phones (unless you decide to root the phone and disable/uninstall/freeze the TetheringManager app.)
Actually what I like is that my bills are even less than $30 per month. Because I am often, many weeks, almost entirely in a heavy wifi environment, I just don't prepay the next 30 days until I really know I need a GSM phone service. Most days I use either GrooveIP, or CSIP to make calls over wifi. If I am not in a wifi area for a few hours, calls go to google voice. AND if I know where I am driving to, I can even use Google Maps when I am not in a wifi zone by precaching the map data in Google Maps. (And even if I don't have prepaid GSM minutes, 911 will still work.)
If you don't pay for the phone number at least once every 90 days, they recycle the number.
For the past seven months, my T-Mobile charges have been $60.00. Not each month. Total.
You know, I probably use less than 100 minutes of talk time a month... But I could easily go over that getting stuck on e.g. a customer service line for an hour or something.
