I have got Samsung Galaxy S2 ( SHW-M250S , with Android 4.0.4) from Korea through my friend. When I inserted Airtel SIM, it recognized this and I got the signal. But after couple of hours it started showing "No Service" . After restart it shows full network and lasts for few hours. I have observed, if I keep my data network (3G) ON , the issue is less frequent, I have observed maximum duration of 15-20 hours phone works fine before showing this problem. I have tried using BSNL SIM but problem is the same. There is no signal issue in my area because the SIM works perfectly in other phones.
I have observed another behavior : during the "No Service" condition, when I try to call some number I get "Network Not Available" error, If try this couple of times, I get signal back but it lasts only for few minutes ( this happens few times but not always). As I have mentioned above, I if restart my phone, it works without any problem for a longer duration.
This is used phone and there is no warranty for this. I desperately need some help to resolve this problem. I hope there is no issue with the hardware.
Attached are screen shots of the software version.
Thanks in advance