Ridiculous charges

I had an amount of R211 outstanding on my water account. I received a letter stating that I should make the payment by the 15th September. I made the payment on the 12 September. I received a new statement on the 16th September that does not reflect the payment made and I am charged a \warning fee"of R149. This is absolute hog wash. How can I pay a warning fee for when I was warned to make a payment by the 15th which I did????? The lady at the office referred me to her manager Mr Philip Bye who is on leave. She says that they work exactly like the municipal offices which I disagree with. Is this kind of billing even legal? """