My dad had a Verizon iPhone 4s running iOS 5.1.1 but using a T-Mobile sim. The other day he gave it to my mom who has a T Mobile straight talk sim, she couldn't get it to work so she gave it to me to look at. I updated it to 6.1 and now I can't figure out how to make it work it is driving me insane, I'm getting all sorts of ways to make it happen online but nothing works. Can some one tell me what I should do? If buying a att straight talk sim works better than I will do that.