My phone suddenly turned off and when I turned it off again there was no signal anymore and the sim card could not be read anymore. I tried another sim and it did not work as well. When I took it to a service center they said something about my phone being corrupted and it was caused by unauthorized apps but I don't know how that can be because I only download apps from the Play Store. Does anybody know any other thing which may have caused it? I bought it only around a month ago.