Poor service

My wifi has been off from the 4th of July up until the 24th of July when I then reactivated my service, I got a message from my bank today stating that my transaction was unsuccessful due to insufficient funds, however I have made a payment on the 24th of July for the month of August , I now received a message saying that my wifi has been disconnected due to non payment, I am upset with the this. And I'm not willing to pay another R400, imagine paying R800 for 1 month on a 20mbs line.