I use an unlocked iPhone 4 with a prepaid data only SIM from b-mobile (Japan) that you have to enter in specific APN/user/pass info for it to connect to the network. After updating to iOS 7 it erased the APN settings and when I type them again then exit, and then re-enter settings, the things i typed disappeared. I tried resetting the network settings as well as doing a profile with the iPhone configuration thing. Still no luck. Any ideas?