Unfair and confusing

I have bought my car in 2017 financed by webank. Their partners contacted me for a maintenance plan which I took . My car got an accident in July this year. The maintenance plan was canceled and a refund was made to wesbank. On Saturday I recieved a statement from wesbank showing that my account is in arrears. I was surprised and shocked to see that because I have never missed a payment, I have never paid less than what I should and I have never paid late ( because everything is on debit order on my salary date) so I called wesbank and I was told that yes my account is in arrears because the maintenance plan did not pay the full amount that they should have paid so I have to pay the difference and I have to pay it in cash . So now you tell me, why are you doing this, why do I have to pay it cash ... when I asked them on the phone I was told that I have to pay it in cash because my car is a write off and I wint be needing the maintenance plan. He further told me that webank paid the maintenance plan company Cash so i also have to pay back cash... so guys this is not fair for me because now i have to pay R1318 rand extra this month coz wesbank need their money in cash even though all along I was paying them in monthly installments with no stress... i feel like it is unfair for them to do that to me and I was never told that I have to pay extra R1318 I just see it with the statement I received.