Airbnb booking nightmare

Airbnb booking nightmare! So a house in Cape Town was listed on Airbnb to be able to accommodate 16people. We booked the house and paid a deposit of R22000. 6 days after booking the host come with added charges saying the booking we made was for one person. If we are bring more than one person he is charging an extra R1700 per head. This is not a B&B and the house was not listed as per room or per person booking. Furthermore our booking was done for the peak season such that if the host can cancel our booking he will easily pick up another booking. Airbnb is not assisting us, they left us at the mercy of this host. The host is refusing to cancel from his side; he wants us to cancel so that we loose R22000 we paid already. This is so stressful especially since our flights are booked already!