BLUU CAR RENTAL BULLY TACTICS

Rented a car from Bluu from the 29/06 to 02/07. When I filled up at the petrol station nearby I noticed the oil sensor light was on. Returned the car, reported it, filled out a statement. Bluu claim I drove over something and the oil sensor was damaged and I was liable for R 3472. I disputed this, got a paid up invoice and my deposit returned. Since then I have rented from Bluu again and was advised when I had left to return the car as there was an outstanding amount. it was late at night, I sent the lady at Bluu Kimberley all the correspondence and then nothing. Now I get a claim from LGR attorneys claiming default judgement etc This is complete bully tactics and how was I to know if it was damaged prior and came loose from my travels. I would like a response from Bluu on how they operate