Towing of vehicle for +-20km - R5000

My son had an accident in the early hours of 7 January 2015. A guy stopped next to him and suggest they call Metro Towing. They towed the car approximately 20km. We went and fetch the car at 10o'clock that same day and Kevin ***) billed me R5073 for +- 20km. His words were: Pay or you don't get your car.<br> Isn't there a standard rate for towing? My friend had her car towed from Potch to Vdbp. +- 90km and paid R1600. How ridicules then this? He also did not give me an invoice. Just a piece of paper.<br> I want an answer from Kevin and if not respond in 48 hours, I will take this matter for further investigation.