Black box. I have a 32" Olevia and a black box keeps randomly appearing in the center of the

Question

I have a 32" Olevia and a black box keeps randomly appearing in the center of the screen. Sometimes letters appear in the box. I don't know how to get rid of it. If I shut off the satellite box and turn it back on, it will disappear for a few minutes and then reappear. Help.
Pat