I have a problem in built previous to 10581 after few days my mobile stated showing no sim card inserted later updated to 10581 now some times it shows when i start phone in some time again shows as no sim inserted... and to get back to 8.1 when i connect to usb cable it dose not detects. shows as slow charging ( tried many cables and other PCs also no use ) but when i boot and when i press power button and top volume button it detects but i dono how to flash the mobile back to 8.1 .. please help