Take a look at the image below. If you toggle all the different menus towards the top, and you don't see the exit button towards the bottom of the screen, you might not yet have found all of your remote functions.
With some cable boxes, you might have more options under the MISC than just what shows up at the bottom. If you scroll to the MISC menu, and in the middle of your screen you see a few dots show up, that means there are more MISC options to go through. You can arrow to, and scroll through, those dots to give you more options under the MISC menu. Your exit button might be there.
The exit button might also show up as "Cancel". Look for a cancel button as well.
Hope this helps!