Every time you connect to a wireless network, Windows saves your connection properties. Here's how to trim unwanted networks from that list and how to prevent metered networks from blowing up your monthly bill.
The more you travel, even if it's only from one coffee shop to another in your hometown, the more likely you are to save settings for third-party Wi-Fi networks.
Windows 10 saves those networks automatically, and if you sign in to your PC with a Microsoft account, it automatically transfers those settings to other PCs so you can sign in without hassle.
If you'd just as soon forget about a one-time Wi-Fi connection, you can do that with a few clicks. Start by going to Settings > Network & Internet > Wi-Fi, where you can find and click the Manage Known Networks link to see your list of saved wireless networks.
Click any entry in the list (1) to expose two buttons. Click Forget to remove that network from your saved list. Click Properties (2) to see settings for that connection.
If you keep a network on the list, use the top switch to tell Windows whether you want to automatically reconnect whenever you're in range. Use the second switch to tell Windows this is a metered connection that you pay for by the byte.
The metered connection option is ideal for connections you set up using your phone as a hotspot, or when using a Mi-Fi device from your mobile provider. When you set a metered connection, Windows shuts down many automatic connections (downloading email and Windows updates, for example), so you don't get a nasty surprise on your next bill.