POOR SERVICE AT ACCOUNTS AVIS CAR RENTAL OR TAMBO

Am so frustrated with Avis/Budget car rental. I paid a deposit when I rent the car even when I extend the booking deposit funds were deducted on my bank account. When they closing the accounts always after returning the car they will deduct the full amount costs while they still holding the deposit..These has been occurring several times and my bank account is on minus accumulating bank charges. Am not sure WHY we have to pay the deposit and car rental funds if they still go back and deduct while there's funds on hold. It really frustrating cause it kept on happening and they will tell you they not sure how did it happen