Avis *****s left right and center

I recently rented from Avis.

I used a voucher I received as preferred customer for a free weekend rental. The booking was made and I was ensured that the voucher was app**** to the rental. When I arrived at the airport I went to the Avis desk and the lady there also confirmed that the booking was free as per the voucher. I also received a free upgrade to group B so I was very happy at this point. I then asked what the cost would be for upgrading to a group D., she quoted me something like R 100 for the two days for the upgrade. I accepted this and thought great, I am only paying for the upgrade R 100 plus additional super waiver of about another R 150 so in total R 250 for the rental. I used a bit more KM than what I got included in the rental which they charged almost R 500.00, this I am happy with as I knew before hand this might happen. I received an invoice for R 1500+- last week and I then queried this with avis, as I was expecting to pay around R 700 in total for the rental not R 1500 as I received the free weekend rental. They just debited it from my account. I attempted querying it with the accounts department and via customer services email. So far they have been spamming me with a notification that says they will get back to me. The lady I spoke with in accounts said she will get back to me, so far nothing.

I am really disappointed with the horrible service. A few months ago I queried why they charged me for more fuel than they actually put in the car and they never got back to me. They are *****ing from me, this is unacceptable.