Extra charged for refuelling

I have been overcharged for petrol. I'm now forced to pay petrol again and I'm being threatened that they will block me and I'm told that my profile has been sent to risk as I often change cars.some of their vehicles are not comfortable that's the reason I often change.i extended for two days and immediately changed the car,thirty minutes later was called to return the car and was away from the branch with more than 200km.now I'm being charged another R850 for fuel and have to pay petrol on the car is was told to return.Hatfield fleet supervisor is very unprofessional and needs to be taken to customer service course.I've been renting for 4 months now and I required my rental statement and I cannot be furnished with.