Budious account figures provided

On 5 Dec 2017 i requested settlements for 3 vehicles, one was with toyota. On 7 Dec i paid the amount as per the settlement letters and on 9 Dec received notice from Toyota that i owed an additional amount as the installment which was due on 1 Dec had not been paid. The other 2 vehicles were handled the same with no such notice. Surely on 5 Dec tbeir system must provide the ENTIRE amount for settlement as the other two did.