Incorrect Debit Order

My vehicle is financed through MFC. I was in Europe last month for work and couldn't receive messages, I saw via e-mail an installment went off I didn't check the amount. Come to find out MFC only debited around three quarters of the installment instead of the full amount.

Then when I returned I got all the harrasing messages and phone calls about settling my outstanding amount. How is that fair, we have an arrangement for a debit order each month for the same amount, how is this my fault?

Last month I waited for the installment to go off with the outstanding amount as we agreed on the 25th, by the 14th of the next month no installment went off. I didn't want to pay it before because the bank would charge me if MFC then deducted it by debit order and it was returned. On the 14th I paid it and ironically starting receiving some more threatening messages.

The outstanding amount of R1500 I couldn't pay afterall since I had to pay my parents medical bills but I am more than willing to settle it the end of the month. I don't think I should have to pay interest since this is not my fault.

How do you mess up the exact same installment amount two months in a row and then harrass your client for the money. This is ignorance and arrogance at an astonishing level. Really really poor service.