Absolute mind blowing bad attitude

Our account nr; PTA 34657 On the 15th of March I paid an amount of R301 to settle the invoice. Due to an error on my side, I used the incorrect ref nr 34757. On the 17th Constantia suspended the water to our unit. My husband phoned immediately and then the mistake with regards to the Ref nr was discovered. He dealt with Annetjie Botes. Low and behold, we receive a new invoice on the 23rd, indicating we are responsible for a Disconnection fee of R860.66. This is absolutely absurd. The account was paid, albeit in and incorrect account for a Mr Tshisikule. Constantia suffered no losses. We are not prepared to pay the disconnection fee, and will take this matter to the Consumer Ombud to note the way in which Constantia operates. I want the amount to be waived and an amended invoice issued.