Don't stick to settlement agreement

I got a call regarding payments on my tv license thats been over due for what I can only guess was for years because I was unaware of one being opened in my name.

We came to a settlement agreement and I paid the amount due before agreed on date. Got sms with amount to be paid and it's been paid now I get email stating that there still R772 outstanding.

These people doesn't know what settlement means or what?