You can deactivate or reactivate the Wi-Fi Hotspots function on your modem at any time. Per default, all modems serve as a Wi-Fi Hotspot. The only exceptions are the b-box and Philips modems that can never serve a s a Wi-Fi Hotspot.
Opening up your modem to other Fon users has no impact on your Internet usage or speed. Indeed, the private part (the one you use) and the public part (used by other Fon users) of your modem are totally separate from one another.
Adjust the settings of your b-box 3 via the configuration menu of your modem or via the Wi-Fi Hotspots line.
Adjust the settings of your b-box 2 modem via the configuration menu of your modem or via the Wi-Fi Hotspots line.