Discovery Bank unusual money deductions without notice

Discovery Bank feels almost like a ****. Credit card related emails of transactions with remaining balance(after deductions) were sent to me after transactions. This is reasonable. They had a system failure and failed to inform their clients, me, that some of the transactions did not go through but then they took it upon themselves to deduct money from the account, still without notice. I was just amazed to see a huge difference in balance between two consecutive transactions that were not even R500 together but there was no shown transaction on my statement for the amounts missing.

I had to call Discovery and be placed on hold for almost 50 min to tell me that they had a system failure which explains the weird account activity of which there's a huge possibility that I could've been double charged. Discovery could've simply sent an email at the time of the system error so clients can be made aware of the situation and how money is flowing through their accounts. They even refused to send an email with an explanation of the implications on my account from their system failure.

Advise, do your calculations for November 2024. That's when the system error happened and there could be some money missing.