Hello, Earlier today, as I went to unlock my Xperia SP, I realised that the screen would not turn on, no matter how many times I pressed the unlock button. I also tried plugging it in to charge to see if the screen would light up then, but the neither the screen or the LED light turned on. It's seems like it's completely dead! I don't really know how to tell if the phone itself is still on, however. It was at about 50% battery. I've had this phone for a little over a year now.

Could you help me resolve this problem? This phone is really important to me!

Thanks!