If you have listings that are no longer active, you have to 2 options
Remove the channel connections the listing has
To Delete the listing itself
To remove the channel connections, Go to Setting > Channel Manager > (select the channel example: Booking.com) and uncheck the box and save. Repeat for every channel & every room you want to disconnect. This will allow you to save per channel connection fee charged by BookingAutomation.
If you delete a room all history of the room is also removed. You may export all its history before deleting the room.