Account paid not updated

I did a manual payment of R400 on the 27th August , the account was supposed to be in credit but I just realized that the account is in arrears with an amount of R81.97 . Can someone please explain how it came about that the account is in arrears whereas I was supposed to be in credit ? I have attached the proof of payment made on the 27th of August to the email , please rectify the mistake from your side .