There should be some overscan. IOW, the picture should extend slightly beyond the border, not stop before it. A test pattern would show if you have a problem.
However, the easiest way to check this is simply use what's in your TV - the scrolling pattern for burn-in protection. It's a rolling black / white pattern that spans the entire display. All inputs are bypassed, so there's no question that the problem is in your display.
Picture Options --> Screen Burn-in Protection --> Scrolling.
Hit any key on the remote to stop it.
If the scrolling pattern doesn't cover the entire screen, call for service.