Charged for wifi I was promised could be capped

after opening an account where I was advised the wifi per month would be capped, I get a statement for over a 1000 rand. After multiple phone calls I then get advised that no capping on an account is possible. Taking this up with the sales manager, all details of the initial call are suddenly lost. I still get emails saying I owe a huge amount that was meant to be resolved. This is pathetic.