unauthorised debit and overcharging

I rented a Ford Fiesta with AVIS registration no. BD62XR GP for a fixed term period of 10 months until 31 December 2015. I was to be charged R100 for each kilometre up to 3000 per kilometre and additional charges if I exceeded. I paid also for a monthly comprehensive insurance. The car was collected on 12 February 2016 after I failed to return it on 31 January 2015. AVIS debited R7638.70 on 3 December 2015 for the whole month of December 2015. AVIS then debited my account with R7815.27 on 1 January 2016 for the month of January 2016. AVIS then debited me R8141.98 for the month of February 2016 though the car was collected on 12 February 2016. My average kilometres travelled per month has always been below 3000 and I had only travelled 1 809 kilometres for the February 2016 period. I requested an itemised statement of account from JoAnne on 15/2/2016 who promised to send it. Nothing received. I want AVIS to immediately pay the R8141.98 back into my FNB account which was debited without proper authorisation as my account was upgraded and my account details changed. Secondly I want AVIS to provide me with a reconciled and itemised statement of account before I can make a payment. Tx