On my 2016 Ram there is a button next to the exhaust brake that you push to disable this function. Also on the computer screen, you can go to settings and program this function when you don't want it to work as well.
Edit...I should have said this function is to turn off the sound....on the computer screen you can set the camera's off as well...there on two on this model, back up and bed camera. These cameras also work when driving, you do not have to be in reverse, just hit an icon on the computer screen and look behind you while driving...but that doesn't sound real safe....