Disgusting service

I used to think the world of mfc until now. My debit order bounced which never happens but I'm having one of those months where I had to fix plumbing urgently and had to use my salary. They called me and gave me the whole schlep of how this was not good for my credit record. I explained that I would make payment in a few days and that I wanted to pay a bit more so I had called their call center earlier the same day to confirm the bank info and ref number I needed to use to make the payment for the extra funds to bring my balance down quicker. This call was before the end of the month but the 2nd of April came and I made payment to mfc and sent the proof of payment via email. During the same morning after I sent my proof of payment I received an sms that I made arrangements to pay on that day and next thing I know they decided to send through a debit order for my car payment. So with the payment I made of R16k and the monthly payments being R5.7k they refused to return the monthly fee even when I explained that I had made provision for another debit order plus had paid the more than twice what I owed for the month. After I sent an email to query and ask them to review and reconsider a refund now they responded and said they need my full info as they cannot trace my query. I'm so over MFC and hope to never have to buy a car again via them. This has been the worst experience over something so small and these companies pride themselves in customer service, I'm disgusted.