Carltex garage ****med me

I went to Caltex garage yesterday at 6.30pm.I stopped at a gas station and and asked for R100 gas and i paid in cash.I stay 2mins from the garage,when i drove off i noticed that my guage was at 9km instead of 64km.i went back after 20mins.Whe i asked for my slip he gave me different slips with wrong times he also refused to call the manager,finally when he got a slip he gave me the one that was a credit card purchase when i paid with cash.He was very rude and defensive even his colleague tried to cover for him,But one of the workers told them to fill my petrol to avoid getting all of them in trouble.I left without petrol and i was threatened to leave, as it is im on 4km i dont even know what to do,I can not go there as the guy is rude and he treatened me.I still have that slip with me should it be needed for this issue to be resolved.