Booking.com review: Booking.com couldn't provide a baby seat and won't refund my money

I booked a car in Rome, Italy with Europcar through Booking.com. I also rented a baby seat for my 6-month-old baby because they offered the option. When I arrived at the rental point, Europcar stated that there were no baby seats left and told me that I could cancel my reservation if I wanted. I canceled the reservation because baby seats are mandatory by law and unfortunately I had to rent from another company with a higher price. Later, I realized that my money was not refunded and I explained the situation in correspondence with Booking.com and Europcar. Europcar states that the money has not been transferred to them. Booking.com persistently refuses to refund my money. They use the contract we signed between us as an excuse. They say that 3 days rent is charged for cancelations in the last 48 hours. If such an option is offered and I have budgeted for it, this must be provided. It is a reservation that I canceled because my situation binds the law and it is mandatory for me to cancel. Even though I said all this, they still insist on not paying. As a result, Europcar directed me to cancel and I canceled my reservation. Booking's representative there is Europcar. The contract between us has become invalid due to their misguidance. Booking.com should urgently reverse this wrong policy and refund my money.