This reinforces my diagnosis of your problem in your other thread: it sounds like your "volume up" key is malfunctioning, and the phone thinks you are constantly pressing it. That would account for this behaviour as well as the constant presence of the volume bar on your screen.
If you can't "unstick" the button I'm afraid it will need to be repaired.
There are "button mapping" apps, but without root I do not know whether any of these could change the function of that button to something else (that did no harm if it were constantly pressed!). But that's the only software workaround that I can think of.