Cellphone companies like StraightTalk actually use a lot of carriers. For GSM, it's mostly AT&T. That being said, are Galaxys purchased from Walmart for use with StraightTalk "locked" in the first place? These phones may have been purchased on sale at Walmart. They were fully paid for. There is no "contract" with StraightTalk. These particular Galaxys do have SIM slots.
So . . . what are the issues?
So . . . what are the issues?