SABC TV License trying to rip me off

I was told that i owed close to R800.00 for my license account of which I made an agreement with them to pay them R150.00 per month until I will be done. In August I was told that it was due for renewal and I told them not to renew it as the TV I had bought using the license was damaged. in October I owed R330.00, of which I paid R150.00 and was only left with R180.00. At the end of November made the outstanding payment by means of EFT. I don't know whether the payment was delayed or not, but a couple of days later I got a sms saying I owed R150.50 in arrears. How do you owe arrears when you've paid an account in full?