Can i use a cspire iPhone on straight talk?

My aunt gave me her iPhone 4 from cspire and cspire phones don't come with a sim card. If I were to buy a sim card from straight talk and put it in the iPhone, would it work? I've read some things about cspire restricting that but I'm not sure. Any answers?

Yes, they recently have brought out sim cards that will work in all the GSM iPhones.

http://wontek.com/How2/straight-talk-offers-sim-cards

Have a nice day