incorrect invoicing, non existent customer service!!!

We were sent invoices on the 31st May for our mini lease which had incorrect kilometer readings, as a result were were charged around R5 000 for an additional 1****m which we never traveled. Firstly we had to ask for the invoices, which Rebecca Raboroko ********** sent us on the 31st May. On the same day I send her a picture of the actual kilometer reading from the car which was waaaaayyy below the reading recorded on the invoices. I asked her to advise where the readings were obtained from since we hadn't receives a call and clearly they don't correspond to the actual reading. She only responded on the 3rd June, saying she was on leave and she would forward the invoices back to the branch to be amended. It's the 11th June today, I've sent about 10 follow-up emails to her with no luck. On the 3rd June I also sent an email to customer services which only responds after 48hrs, I've since then received a response from 2 different agent who can't seem to help. This is completely unprofessional as we are now charged for incorrect "extra kilometers' and the customer service is non existent. I've yet to be assisted since 31st May. Completely unacceptable.