Dispute mechanical damages on hired vehicle

Hired a vehicle from them, day 2 driving a vehicle, the car displayed a low coolant fault, reported the car to their customer service, some response were just drive its not a serious thing, some said go to any garage and put a coolant,some just go to the nearest branch and I told them the nearest branch is Port Shepstone and I'm in Mount Ayliff which is +-150 km, ultimately I called the King Shaka Airport branch where I picked the vehicle from,requesting them to allow me to take it VW kokstad for coolant fill up, we agreed, when I got there VW kostad, the Technician took it the workshop for check up, he then came back and say they need to send the vehicle to Margate VW where they are well equipped for further investigation, now Europcar came back with the report from VW that the radiator was damaged, and that I must pay for those damages yet the technician from Kokstad VW that there is a foreign coolant inside the vehicle,yet I never top it up,meaning the previous renter did fill the coolant,with the leak that was identified it means the foreign coolant was getting finished hence the fault displayed. Now the Europcar has handed over to lawyers yet I have been disputing these damage. Please assist.