Double Payments and False Cancellations on Booking.com

I booked a property through Booking.com and received a message from the owner stating she was fully booked and didn't understand how my booking went through. She offered to accommodate me if I paid an additional amount directly to her, which I declined. I requested a refund through Booking.com, but she falsely claimed I chose to cancel, resulting in no refund. When I followed up with Booking.com my call was cut and they removed my booking number and pin from their system so now I cannot call/query this booking online. Not only is the property owner a *****, but the site too.