MFC demanding the instalment for settled accounts- date settled account (16 november) and instalment date 20 november

I used to pay my vehicle finance on 20th of every month. I requested the settlement quote on the 10th November 2017. I received the settlement quote which was valid for 7 days . The quotation was valid up to 17 November 2017.The settlement amount as specified on the settlement quote was paid to MFC on the 16 November which is within or before 17 November. On the 20th of November, I got sms notifications from my bank about MFC vehicle instalment paid. I called my bank and they advised me to reverse the payment if the vehicle account is settled and I reversed the vehicle instalment because it was settled on 16 November 2017.

MFC has sent letter of demand,saying that I defaulted and demanding me to pay the instalment 20/11/2017 of the car that is settled on the 16 November 2017

please see the extract from MFC settlement letter

With reference to your enquiry on the above-mentioned account, we confirm that the settlement will amount to R 356477.01, including daily interest and an amount of R 85 inclusive of VAT, being the cost of couriering the vehicle registration papers to you. This is provided that we receive it on or before 17 /11/2017. This amount takes into account all payments received on settlement date including the payment on 20/10/2017 for the amount of R 6720.43 and assume no cheques/debit orders will be referred back to us by your bank. Should the above payment be returned the settlement figure would have to be revised. This settlement amount includes all arrears or advances on the account at date of settlement quotation.

please see the extract from MFC settlement letter

With reference to your enquiry on the above-mentioned account, we confirm that the settlement will amount to R 356477.01, including daily interest and an amount of R 85 inclusive of VAT, being the cost of couriering the vehicle registration papers to you. This is provided that we receive it on or before . This amount takes into