Very bad dealings with towing company

My son was in an accident and a towing company showed up saying that they were sent by insurance to collect vehicle. Turns out they were lying and we had to pay just short of R9000 (3days) to have the vehicle released. We paid it and when asking for an invoice and receipt we were told to stop harassing them. That is not how a business is run. All I want is a legal document showing what the charges were for and also a proof of payment from his side.