To permanently turn off a VPN on your iPhone, you need to remove its configuration profile from your device, as simply disconnecting can leave it able to reconnect automatically. First, open the Settings app. If you are using a VPN app, scroll down to find that specific app and toggle off any "Connect on Demand" or similar auto-connect features, then go back to Settings. Next, go to General > VPN & Device Management > VPN. You will see the active VPN configuration; tap the "i" icon next to it and choose Delete VPN. This removes the profile entirely. For any VPN installed via a configuration profile, you would delete it from the same "VPN & Device Management" section.