Finchoice generating ghost amount just to collect extra

I paid off my account at Fichoice and it was an immediate payment on 27th September. Then on the 1st or 2nd of October they called me saying my account is in arears of R200. I told them i paid off the account. They can see i was owing 1500 and paid the exact amount but they calling m that I'm owing them R200. Where does that R200 comes from?