hey guys, i'm facing the same problem as all of u.. cant make calls/sms nor receive calls/sms although my damn signal bar is full.. basically, i restored my iphone more than 10 times each time this problem occurs.. so far, i've tried many things to get this problem fixed.. any how, so far my iphone is running pretty well for 4 days now since my last restore..this is what u guys can try, no promising that it can fix the problem, maybe the problem might occur again, but so far mine is running well:)

1. update ur itunes with the lastest version, and what ever needed to be updated in ur itunes.
2. in ur iphone, go to setting > general > date/time > turn off "set automatically > then set the time zone manually according to ur area.
3. go to general > reset > reset all network
4. reboot ur iphone
5. and now, restore ur iphone with the itunes which u just updated. update any carrier settings if there is a notice pop up.

pls update here if this steps works for u all.. anyhow, i just share what i tried and so far so good:) lets pray that it works for all:)

arafat : its the same problem:) at first its no servise/searching for signal, then after on/off and turn on/off airplane mode, it shows signal but cant make/receive calls and sms:) i've read through everyone's comment here, and some is facing this same problem, so its just a try out for u guys:) it may or may not work, but no harm trying:)