I'm new here. I have an iphone 3gs from At&T I've purchased the sim and airtime card from straight talk. Ported my number. Everything went find. But I could not use get data usage because I could not change/access the apn settings. I downloaded and used a program. I turned the wifi off, the 3g on and rebooted. So now I have my 3g. I can use safari ok, but I can't send or receive MM text messages. I also cannot download from the app store. Please help I have been up all night with this.