Evri complaint: Lost International return

I sent a parcel return to Italy at Post Office branch. Post Office chose Evri service which cost me £11.95, the contents of the parcel (a pair of shoes) were worth 64.99 euros. When booking the parcel at the Post Office counter I provided my email address, return postal address and a phone number. Paid all the fees, filled in customs declaration form. The parcel never arrived to the vendor in Italy. When I checked the tracking, apparently the parcel only got as far as UK border where some taxes and duties were requested to be paid. Nobody contacted me about it so the parcel was ‘returned’ except it never came back to me. when I contacted Evri they said it needs to be dealt with by the third party who arranged postage, i.e. Post Office. When i contacted Post Office they said it needs to be dealt by Evri. I paid insurance for the parcel. Neither Post Office or Evri admit it’s their fault. It really is an appalling service from both Evri and Post Office.