I'm over-charged.

I really fail to understand how they bill. I moved in June 2018 and my water and sanitation bill was R200. for July it was R781 and I paid it on the 31st July 2018. Today is the 14th August 2018 and I was billed R860, like I don't understand, Have they already predicted that my bill for this month is R860 or are they saying that between the 1st and 14th(today) my bill is already R860.