Unfair booking treatment

I made a booking via booking.com for 10 guests in Sea Shell Cottages in Port Shepstone and only to receive an message from the above place via booking.com messaging system that we are double booked and our booking is cancelled. Firstly the Sea Shell Cottages never professionally addressed this matter. The first cancellation messaged from the place had no greetings and also no apology, the just say d to us that there were doubled booked and our booked is cancelled that it. We were never offered alternative dates, after we raise that they started to ask things. This place is not the professional place for people to stay.