I know this is the wrong place, but I bet someone knows - Smartphone question ... [View all]

I leave wifi on for my smartphone all the time in the house, and it's connected to vpn, as a vpn app on the phone. When I leave the house is it really necessary to disable wifi on my smartphone. I've never seen a definitive answer. As the phone has vpn as an application, I don't see this as a problem. Am I wrong? I'm always wondering if it might connect into some rogue hacker network that does not ask for a password, and maybe my vpn app fails, which it does sometimes. Thanks!!!