I'm blind and I could call people whose numbers I know even on a dumb phone with no accessibility. At the moment, some strange failure of the phone screen reader, accidental switch off of volume or whatever and it is game over. Try to restart by the hardware keys and pray that you are not left with a thousand dollar brick in the middle of a trans-continental trip. Real story with my first touch phone with the only difference that at the time I didn't know the hardware keys to restart the brick.