I was charged an additional €120 after a prepaid rental. Customer support first told me it was VAT (despite VAT already being included), then, after calling them out on this, they said it was for an extra rental day, despite my return receipt showing the vehicle was returned on time. After providing the documentation, I received no further response.
So, basically I was given contradictory explanations for the charge and that the supporting documentation was apparently disregarded.