How to end call without using side button

When I get an incoming call and I wish to end the call, I am not able to do it as there is no option on the touch screen to end the call. I have disable the side button to end the call as I have a habit of pressing the side button to lock my screen while on call. Since side button is out of option, I cannot end the call, I have to wait for the call to end by itself. Please help to suggest some way so that an onscreen option would come to end the call.