Horrible communication and customer service

I've financed 2 cars with MFC. They give disgusting customer service. My salary date is the 25th and therefore I arranged for my debt order to be made for the 25th. I waited for the debt order to go off for my car. It never did. On the 1st I received a message from mfc saying I'd been handed over to their collections department. When I checked, mfc had attempted to debt my account on the 24th. I phoned mfc and after 47min on the line, I was able to make an eft payment. The next day they sent me a very rude email warning me to pay them. I attached my proof of payment to this email. And at present I keep getting calls from them threatening me to pay. But I have a proof of payment. And this whole mess is their fault as they debted on the incorrect date. Really poor customer service. I will never finance anything through them again.