Lack of urgency and very poor service!!!

Mercedes-Benz Financial Services South Africa is giving me a very bad service. I was overcharged on my last instalment. I wrote an email on the 8th of May 2024 where I was given my paid up letter and an apology that R6 665.62 was charged by mistake. The same would be refunded within 14 working days. To this day no refund has been done. I have followed up several times and I am told there is an IT issue.How can such a big organisation fail to fix an IT issue for more than two weeks. I have followed up on emails and uncountable phone calls as I have been tremendously inconvenienced. I am totally disappointed as I used to regard this organisation as highly reputable. When I called today , I am told that they do not have any timelines as to when the payment will be done. If it was me who had skipped instalments , I would be receiving summons and all sorts of legal punishments. Mercedes-Benz Financial Services South Africa has shown me how poor their services can be. Am totally disappointed at the lack of urgency and no care for that I have been shown