Lenovo — lenovo a6020a40 camera problem

Sir in my mobile camera application there is no option to change front camera to rear camera. So only my mobile front camera working .Please help me to suggest what I have to do with the camera application to short out the camera problem of changing from front to rear camera .In my camera application only 4 option available 1setting in which aspect ratio and photo mirror. In down the screen face beauty camera and video camera . Plz help