How to Remove Saved Networks on an iPhone
The Apple iPhone, like most devices using Wi-Fi, is designed to save your network settings so you don't have to re-enter your password every time you want to access the Internet. While this is normally a handy feature, it can become problematic. For example, if you accidentally join a Wi-Fi network that you are not sure is safe, it's better to make the iPhone forget the network altogether. After removing a saved network, you always have the option to connect to it again later.
1 Removing a Network
To delete a saved network on the iPhone, launch "Settings" from the home screen and then select "Wi-Fi." If you tap the "i" icon beside any network name that you've joined in the past, all of that network's details appear on the screen. Select "Forget This Network" and the network information is deleted from the iPhone's memory. After removing the network, it still appears on the list of available networks, but the iPhone won't join it unless you specifically select it again.
Information in this article applies to iOS 7. It may vary slightly or significantly with other versions or products.