I can't seem to turn the key touch tone off. The instructions manual says that it is turned off by touching the symbol "♪" located on the last line of the screen. It also says that when the key tone is turned on, the key tone indicator ♪ will be displayed in the 4th line of the display. Right now it's on, but I can't seem to turn it off, and it gets annoying especially when I'm the only person in a crowd beeping while typing something. I keep pressing the symbol "♪" but nothing happens, and I know that the grid that the ♪ symbol is, works, since I can switch to the alarm mode and press it to turn the alarm on/off. Maybe it's just this unit that's like this, any help will be greatly appreciated.