using postpaid phone and sim card for new prepaid plan

[picabootori]

I used to have a tmobile postpaid plan last year, then canceled the service. I want to know if it's possible to use the same phone and sim card and switch over to a prepaid plan??? All the prepaid kits I see on ebay come with a sim card :confused:

Thanks

[picabootori]

note: I will be using it in the US

[tzsm98]

The phone will probably work, the SIM will not. I bet you get a very precise answer here shortly from some one who actually does this sort of thing all day long. I'm going just by what I've seen happen in the lives of the folks around me.