Harassment and ******* Charges

This company calls me at least 5 times a day every day, Sat and Sunday included. I then get billed for this. I have made arrangements for the payment and have stuck with it, just to be called again. And today I was told that I am being billed R20 for each time I am called. I have never agreed to this and this is eating up all the money I am paying, so only way get rid of them is to settle the account. I am not going to pay 1 cent further until someone with authority calls me and explains to me why and how this works. I am more than prepared to go to court if needed.