Nedbank refuse to get back to me after several call to them

Late last year I contacted nedbank to change my bond loan repayment amount. They failed to do follow on instruction. This lead to me having to repeatedly call them again, wasting my time and money on calls to the call center. I have requested them to refund the fees paid by me for calling the call center (which would not have been necessary, had they followed on the initial instruction) - and after several of these requests, they have as yet not given me any feedback. So I'd like to know why I have to waste my time and money calling their call center for mistakes on their side? Seems (once again) that this is the only real platform to get responses from corporations.