Samsung S500i turns itself on
The other day I turned my old Samsung S500i off to conserve the battery. When I came back to it the next day the battery was empty. I discovered that the phone had switched itself back on automatically. After recharging the battery I again switched the phone off but in a couple of hours I heard it switch on again. This has now happened about 8 times. The only clue that I have is an icon that has appeared on the screen that I have not seen before. It is a white R on a green background. This may be unrelated but I can't find any reference to this icon in the user's manual.
Any ideas? All suggestions will be gratefully received.