How to Check for an Enterprise Provisioning Profile on an iPhone
Go to Settings -> General and scroll all the way to the bottom. At the very bottom is "Reset". Above that is "Regulatory". Above that is "Profiles". If you have no profiles installed, this may not show up. In that case, you're fine. If a profile does come up click on it to get more information. The information page will tell you the name of the profile and who it's licensed to, like this: