I made a booking through booking

I made a booking through booking.com and I also used my credit card to pay through them. Arriving at the hotel the hotel told me there was no payment and I have to pay before check in. I paid , just to realise a few days further I paid double. Booking. Com and the hotel. Booking.com did pay the hotel. So I went to the hotel for a refund. They gave me a refund but at the same time charged me again on my credit card. They still have my money and I struggle now to get my money from them. Can you please advise what to do?