FIRSTCAR RENTAL NOT TRUSTABLE

We rent a car Firstcar rental Kingshaka Airport by return we filled the car fully at the garage at the airport gave a receipt to them showed it is refilled they invoiced me by also fill the car with R 216 petrol same day and charged me for this added 10km the garage is not a km away complained to them they told me the VW polo have airlock and it does not fill completely...they are a bunch of ****ers never ever again