Booking.com pathetic customer service

We booked an accomodation at The Cape Villa through booking.com in October 2017. We paid the 50% deposit to the owner in December 2017 as required and stated on the booking.com website. On the 30 October 2018 upon enquiring about our booking, we find out that our booking was cancelled back in February but we were never notified. Booking.com claims they sent us an email but after checking with our provider, there is no evidence of their email being sent or rejected by our email provider. They did not call us either even though they had our contact number. They are refusing to find us alternative accommodation, and refusing to pay the difference between the new accomodation that we have to find ourselves. They refusing to take responsibility for not notifying us but want to offer 50% of the price difference between the old booking and the new accomodation we might find and only when we check in, in December will they compensate us. Had we known earlier, we could have found alternative accommodation. Booking.com has successfully managed to mess up our family holiday that we have been planning for the past 2 years.