Avis WORST EVER

Pitty you have to rate them at all!!!!! I have just been billed without any notification for an amount that's been pulled out their ****! I returned my vehicle over a week ago without any damages and a full tank and have been charged R2000 more than the amount that was due on the rental! No invoice received beforehand for this amount. Is management at Avis sick or just f*#@ing stupid!