I have a Sony Xperia phone. I updated it to Android 4 and since then I couldn’t make phone calls or send messages. I tried to repair it with the PC Companion but nothing has changed!
checked the network operator settings?
Another thing to look at is the APN (access point name) settings and the Network Operator setting to see if they are correct. If they aren't, then your phone will not connect to your phone provider's network and you won't be able to make calls, send messages, or use the mobile data. Go to Settings, Wireless and networks, Mobile networks, then Access Point Names/Network Operators (or something like that). Do a search online for the APN settings for your carrier and phone (like this http://forum.xda-developers.com/showthread.php?t=1737589 for AT&T).
Did you use an official update for ICS or did you flash a custom ROM? If you flashed a custom ROM, look for a compatible kernal for your phone that works with ICS. I've had similar problems because of using Ann improper kernel for my phone with a custom ROM.
you have to change mobile network from 3g network to 2g network . i was suffering from same problem now i have solved by the above step
Have you tried downgrading the phone to the previous version of Android? I'm not sure if you have root or whether this was an official Sony firmware update. If it's an official update, then you may be experiencing some of the unspecified problems that Sony has publicly acknowledged.
However, if you flashed an ICS ROM, try the thread below for more information on how to downgrade to an older version of Android: