I have xperia p. It sometimes says switched off when other tries to make me call.Also i can`t able to make call & on display it shows calling,but there is no dialer tone.The network operator range is excellent.The cell fails to search mobile networks in settings. It happens randomly in a day.Whenever this problem arises i restart phone or swich to airplane mode & back to normal mode & problem gets solved.I update my os to 6.2.a.1.100,but problem is not solved.