How to forget a wi-fi network on your iPhone and iPad
While in range of the wi-fi network you want to forget, you can do so right on your iPhone.
Launch the Settings app.
Tap the info button next to the wi-fi network you want to forget. It looks like a lower-case I.
Tap Forget This Network.
Tap Forget when prompted to confirm you want to forget the network.
How to make Windows 10 forget a WiFi network
Once you have connected to some wireless network in Windows 10, the operating system will remember this network and will try to re-connect to it once it is in range. If you have a reason to no longer connect that network, you can make Windows 10 forget that network. Here is how.
To make Windows 10 forget some previously connected wireless network, you must delete the profile which the OS creates and stores for the network. This can be done using the new Settings app which comes bundled with the operating system and replaces the classic Control Panel.
Do the following:
Open the Settings App from the Windows Start menu.
From the Settings App, go to Network & Internet. Then click Wi-Fi
From the "Wi-Fi" menu, you will find a link that says "Manage Wi-Fi settings" on the right. Click it.
Under "Manage known networks", click the stored network name you want to remove. After you click it, you will see the "Forget" button. Click it to make Windows 10 forget that specific network.