Numerous attempts to sort out/query an issue from last year

Europcar had a claim for an accidentlast year. I have tried to query it through every channel I can imagine. Called your branches, emailed the branches, called customer care departments, emailed the departments. Looked for contact details online, found none so went through an online form. I have had no response as yet. I am being called by a collection agency - but I am still trying to clear up the validity of all the charges. Other than this - I enjoy interacting with EuropCar. Their service at the rental desks and booking process is enjoyable, it just seems that when the chips are down that the lack of depth in their support shows through