How do i get a cellular data network on IPhone 3GS?

[kaay;D]

Okay, well me & my mom are retards with tech & for christmas I got a IPhone 3gs from Game Stop. They said it was unlocked but the phone is useless without wifi. its a at&t phone but game stop I guess sells them.. anyway at the top it has signal, and after that usually it says at&t right? Well mine says "HOME". Now I don't have a plan with at&t because its like $90 a month so I went with net10. All they gave me was a account for net10 and a new # for the phone. Okay now with the problem, With or withought wifi I can send pictures, or have a group message. And I sent a picture to a friend who had a iphone, so I can only send pictures to people who have iphones. Withought wifi I have no internet access what so ever. No facebook, safari, itunes, app store, maps, weather, youtube, and most off my apps. When ever I try it says: "Could not activate cellular data network" and that I'm not subscribed to one. I asked my mom about the "personal hotspot" but she said we have to have a plan or w.e with at&t. My mom has a friend to try to jailbreak it to see if it helps, probably won't, and I updated it to 6.0.1 I don't know if I need to downgrade it or something & I don't even know how to do that either. I don't know anything about the phone. I called net10, apple, and gamestop and went to all stores they don't know what to do. Please help me.

[MDawn]

You need to talk to you carrier if you dont have a signal. I have no idea what net10 is but I assume thats some type of small carrier in you area.