Bought my new Iphone 4S 64GB overseas and on return to Namibia, found that its service is interrupted numerous times a day giving a "invalid sim" notification. Service can only be regained by rebooting the phone. Lately its hangs during the 'unlocking process' and required another reboot to overcome this problem. I already reset it once to its original settings but this did not solve the problem. Being an executive businessman I must rely on my phone - and desperately require assistance for my phone.

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