If ever you haven't tried resetting the camera, please try it first. It's possible that you or somebody using the camera may have set something on the camera's setting to have this result ( this is based on my own experience :D ).
Anyway, here's how you reset your camera:
This will basically set the camera to default settings. If there is no hardware problem with the camera, this will correct the problem. However, if the problem persist after the reset , you may want to bring the camera in a service center for repair.
I hope that helps.
Good luck and have a nice day!