Once you enter the password for a particular wifi network, this information is saved on your iPhone or iPad. Every time the device gets within range of a remembered network, it will automatically connect if wifi is enabled.
When several remembered networks are in range, it can be difficult to connect to the desired router. In order to prevent your iPhone from connecting to some of these networks, you can “forget” them in the iPhone’s Settings panel.
Tap on Settings from the iPhone home screen.
Scroll to the top of the Settings menu and tap on Wi-Fi.
In the Wi-Fi section, there is a list of nearby networks with a check mark next to the one your iPhone is currently connected to. To forget a particular network, tap the Blue Arrow next to its name.
The next screen will give you detailed information about this network. Scroll to the top of the menu and tap Forget this Network. The password information will immediately be forgotten and the iPhone will no longer connect to this network automatically. The network will still be visible in the Wi-Fi settings menu if ever you wish to reconnect to it.
