Extremely poor customer service - no response to communication

Extremely poor customer service after minor damage to a hire vehicle. Despite Superwaiver cover taken, and full and honest disclosure of all details associated with the damage (including 3rd party contact details), Europcar did nothing for almost one month and then promptly handed me over to collections. No refund provided and now varying additional amounts demanded from both myself and the 3rd party. Other than sending threatening emails, Europcar simply do not work with the customer to provide clarity on the way forward. Complete lack of coordination between various Europcar staff, and no oversight of the process. It is impossible to get responses to emails (no response to emails sent on the 05, 12 and 19 July 2022), the phone number for Collections ***) simply rings and rings without anybody answering. I am at a loss on how to proceed and escalate this concern.