Yet another banking institution failure

This is a fight that has been going on for over 2 years now between me and Dashpay/Nedbank. On 31st of March one of our daily credit card "batches" was not paid over into our account from these 2 institutions. I don't know who is ultimately responsible, but initially I was passed from one company to the next and back again. Each one insisting that the other one was responsible. Then they refused to admit that the "batch" in question even existed, even though it was clearly missing. At the time I didn't have the actual credit card slips - due to lockdown and staff changes etc. But I had proof that it did exist. But they both kept telling me it didn't exist and they couldn't find it on their system. Then I found the slips. I sent them through, and they accepted that the batch did in fact exist, and, hey presto, they found the info on their side. Then after months and months of emails back and forth and me demanding our money, they said that my company would have to agree to pay any fees that may incur, and accept if any of our customers refused to pay the amounts after such a long time. I refused - how is any of this our or our clients fault. We pay these 2 companies a lot of money every month for the privilege of using this service, surely they pay some of this to insurance to cover these eventualities? So eventually they paid us our money, which they took from our clients accounts "through the back door". And now, understandably, one of those transactions has been reversed. So basically because of their incompetency and basically, what seems to me, fraudulent behaviour, the only people suffering are us and our clients. Not the people who made this error. How do their "books" balance at the end of each month? This isn't the first time this has happened to us, and I am sure we are not the only ones this has happened to.