Question about the At&t "GOPHONE" windows smartphone.?

Im thinking about buying a Nokia Lumia 520 GoPhone, im currently on a family plan, using an old crappy phone for the while with a AT&T family plan with unlimited texting and phone, but i dont have Internet, Since its a smartphone, which i guess requires data plans, can my sim still work on it? Since i would be running the internet/data wise stuff from the smartphone with my WIFI. i heard it'll just say No Network Connection when im outside my WIFI zone. So the question is, will my sim card work on the phone still using my unlimited texting and phone feature through my current plan, and will not require me to get on a data plan due to me only wanting to use the internet/data through my WIFI from the WIFI feature through the smart phone?