Hello @Kaydee2
You're right, third party bookings are not allowed unless the booking is made via "Airbnb for Work".
AND as such, a review has to be deemed relevant and based on a guests personal experience, which is impossible if they never stayed there! You even sent them the official Airbnb link that says exactly that - good for you but unfortunately you fell on a CS rep who is untrained and useless. Call again and you have every chance of speaking to someone new and hopefully more knowledgeable than the last person! Have that help link handy again and if all else fails, ask to speak to a supervisor.
After having written this I decided to go and check this bad review but I can't see one so maybe the review has been removed?
Good luck and keep us posted
Joëlle