Booking.com Fails to Issue $135 Refund After Europcar Reservation Cancellation

I booked a rental car from Europcar through Booking.com to use on Chios Island. I made the payment of $135 using my credit card around May.

On July 23, I canceled my reservation, and the system stated that the refund would be processed within 7 days. However, even though 20 days have passed since then, my $135 refund has still not been credited to my credit card account.

Although my cancellation through Booking.com was officially confirmed, I am being inconvenienced due to the failure to process my money. I demand that my file (No: 798741429) regarding this canceled reservation be reviewed urgently and that my delayed $135 payment be refunded to my account as soon as possible.