Fake listing - beware!

This may very well be a false listing, but are you saying you have a written contract with the building owner stating that all listings in the future will be listed with you exclusively? Or do you just have an "understanding" with the owner? Because in general the way it's done is that there is an individual exclusive given as units come on the market. Also, if someone decided to sublet a unit, there is no way of forcing that person to use a particular broker to do so.

Yes, I have a written agreement covering this entire building, and there is no such apartment "D4" in the building (photos on a previous fake listing by this same real estate company are not even of an apartment in this building). Furthermore, any sublets require the owner's permission, even though this may not be unreasonably withheld, so I would know of any such availabilities.