On Demand is in the main menu structure of that particular device. There is no way to uninstall and reinstall just that application by itself. That means the only way to fix this device is a hard reset which will also make you lose your contacts and other apps as well as text message history. But, if you bring it to a Sprint Service & Repair Center they can back up your contacts and then perform the hard reset and confirm that fixed the issue. In this way you will avoid losing your contacts.