Stop taking our money

Ive been spending R 3000 daily on the Courier guy sending parcels. Everything is measured and weighed on our side and booked online for pick up. Again yesterday they overcharged us by almost another R3000. No response from anybody as of yet. Even spoke to the regional manager. Not the first time this has happened. I then have to explain every send item to get a refund which takes 10 days before I recieve my credit.Courier guy you are pathetic. You've just lost a big client