My wife just complained that she no longer can answer calls the one she has since she owned this phone (and every other). 

When a call comes in, there is a little indicator in the top row by the clock and battery indicator that flashes, rather than a full screen notification with a green and red button. 

I've had a look at all the things I typically would expect to see settings under, but there is nothing. 

Anyone seen this and know how to get it back to the default?