Ballito Accommodation "free cancellation policy" not so free when you cancel

I booked holiday accommodation which was advertised on Booking.com by Ballito Agencies (27 Apr to 2 May). The ad was very clear that there was a FREE cancellation policy, if cancelled before 28 March 2022. I called Ballito Agencies before making the booking to confirm that they existed and everything was kosher - they confirmed the free cancellation policy and that if I changed my mind within 48 hours they would not collect the 50% deposit from my credit card. So I made the booking. Within 24 hours the deposit was collected from my credit card. Things then changed on my side and I decided to cancel my booking. Then I received a message from Ballito Agencies through Booking.com that they need my bank details to refund my deposit minus R400 booking fee. I called then to enquire about this, but they said Booking.com doesn't allow them stating this "non-refundable administration fee" which you do pay if you cancel your booking. Just to get the bulk of my money back, I reluctantly gave my bank account details but I would like to warn holidaymakers to be aware of this.