The best way to avoid a room being booked by more than one guest for the same date is to keep an eye on your rates and availability.
You can check all your room rates—as well as open, closed and sold-out dates—by opening the Rates & Availability tab on the Extranet.
If you get a booking from another website or OTA, make sure you close or adjust your availability on Booking.com. If you work with many other platforms and OTAs, a channel manager might be a great way to manage your rates.
For more info about working with channel managers, click here.