Hertz Rental Car

We travelled within Spain. Hiring a Hertz car in Serville October 11th to 17th 2023. They insisted on a further deposit of 500 Euro. Hertz say they have paid back but they haven't. They ignore request to show proof of Payment and Keep going in circles supplying same paperwork over and over. One cannot get past customer service to deal with the issue. is this a Hertz worldwide norm. Who do we get help from? who do we go to get this sorted and refunded. They have de*****ed us. They say they have paid back 527 Euros but hey have not, so who did they pay? They wont tell us. ref Ref. No: ***1