You can't make American calls after Apple's mobile phone is updated. What happened?

2. If you shut down and restart, there will be another situation-there is no service, which is even more embarrassing. It took me a long time to find a way to recover. At this time, first hook up voice roaming, data roaming and CDMA international roaming, and then open the flight mode. After a few seconds, you will be prompted that the iphone cannot be activated. Just turn off the flight mode at this time. This method may not be successful once, just try it several times. If feasible, repeatedly turn on and off voice roaming, data roaming, CDMA international roaming and flight mode. When the iphone is reminded that it cannot be activated, there is usually a signal. (When there is no service, the operator under cellular mobile data is blank. When there is a signal, China Unicom will be displayed below. Remember the signal and try not to turn it off. After restarting, there will be no service. )

3. After the signal, you can make phone calls and receive short messages on the mobile network, but you can't send short messages. I haven't found a way to send text messages yet. If you really want to send text messages, you can download "Yixin", and it is the same to send text messages with this software.

4. Finally, remind the person who bought the so-called American version of unlocked 4s to confirm whether it is a built-in card version (in fact, most of the so-called cheap American version of unlocked 4s on the Internet are built-in card versions). If so, it is best not to upgrade ios7. Since Apple has closed the certification of ios6. 13, I tried to upgrade to ios7, and I can't brush it back. After the upgrade, you can only make do with it.