The process to forget a WiFi network on an iOS device, such as an iPhone or iPad, is as follows:
- Go to Settings > Wi-Fi
- Tap the information icon next to the network to forget.
- Select Forget This Network.
- Select Forget to confirm.
If your device is unable to forget the network, it is likely that you have a profile set up, to remove this:
- Go to Settings > General > Profiles or Profiles & Device Management
- Select then remove the profile.