TEMPEST CAR HIRE IS DECEPTIVE.

I made 2 bookings in may 2023 for december 2023 and march 2024. I have my confirmation email. When i viewed the booking online tempest car hire has changed the super cover to standard cover and the rental cost as well. How is this possible?? I have CONFIRMED reservation numbers and EMAIL . How do i go forward from here. I have been loyal to both tempest and europcar. I cannot accept that tempest car hire can amend my future booking without my knowledge.