Incorrect Billing reference ***2

I have app**** for ADSL in the February 2015, my bill was always R579, untill i cancelled my debit order, which was my previous complaint because Telkom debits on the incorrect dates. So I decided that I will pay them myself monthly to prevent being debited on the wrong dates. I made a payment of R579 on the 22nd of July 2015. But now my statement for Auguste is stating that I must pay a bill of R744. This is so messed up, because when I speak to customer service, they keep on telling me that they will resolve it, but can give me no guarantee, and that is should phone back in 10 working days. I phoned again yesterday, and they said they are still working on it, and that it could take longer thant 10 working days. They also advised me that I should only pay R579 and do not have to worry about the mistake. I would do this easily if I have it in writing or they can send me the correct bill. Simple stuff like this makes a person so angry, you sign up for R579 and then it changes to R744. I know no one will contact me, because my previous complaint was also ignored.