Wrong Amount Deducted

I know in this country you can't expect too much, but basic things like the correct debit amount is one thing that is not supposed to go wrong. My monthly bill is supposed to be R287 per month as I have a prepaid top up account. Conveniently, this morning, the amount of R475 has been deducted. WHYYYY??? I tried phoning their wonderful customer service, but after holding for 49 MINUTES I couldn't take it any more. How do you deduct the wrong amount?? Why am I supposed to be happy about it? I expect this issue to be sorted out before the end of the day. Twice this year the wrong amount gets debited. No more. Either this gets sorted out today, or I will take it further.