Here’s how to disable Wi-Fi on D-Link 3782 routers:
1. Using a computer connected to the D-Link router, open an Internet browser and type 192.168.1.1 to log in to the web-based control panel.
2. When prompted enter the password: admin (lowercase).
3. Click on Setup tab (top of the page) –> Wireless Settings (on the left side) –> scroll down to the bottom of the page and click Manual Wireless Network Setup –> uncheck Enable Wireless.
4. Click Save Settings.
NOTE: If your router is Dual Band, you need to disable both the 2.4Ghz and 5Ghz wireless bands.